MCAT Organic Chemistry Exam Review: Key Concepts and Solutions for 2024, Exams of Nursing

Download MCAT Organic Chemistry Exam Review: Key Concepts and Solutions for 2024 and more Exams Nursing in PDF only on Docsity! MCAT Organic Chemistry Exam Review Question with latest Solution 2024 What are the four rules for writing resonance structures? - Correct Answers ✅1. Atoms must not be moved. Only electrons. 2. All resonance atoms must lie in the same plane. 3. Only valid Lewis structures are allowed. 4 . The number of unpaired electrons must remain constant. What are the two conditions for resonance? - Correct Answers ✅1. An atom must have a P orbital or a lone pair of electrons. 2. It must be single bonded to an atom that has a double or triple bond. The latter compromise conjugated unsaturated systems. Huckel's Rule - Correct Answers ✅Planar monocylic rings with (4n+2) Pi-electrons must be aromatic (have resonance). What is the condition for a chiral center? - Correct Answers ✅First, the participant in question cannot be a halogen, a CH2 group, an Oxygen, a Halogen, or any Carbon participating in a double or triple bond. MCAT Organic Chemistry Exam Review Question with latest Solution 2024 Then list the groups attached to a Carbon. They MUST be four different groups. If the conditions are met, then the Carbon in question is a chiral center. How do you determine Absolution Configuration? - Correct Answers ✅First, prioritize the atoms in terms of atomic weights (if two atoms are the same element, then their substituents are compared to determine priority. Substituents on double and triple bonds count 2 and 3 times, respectively). Now, rotate the sigma bond of the Carbon so that the lowest priority group faces away. Next, order the numbers in terms of increasing priority. If it increases clockwise, then the atom has "S" absolute configuration. if it increases counterclockwise, it has "R" absolute configuration. Does absolute configuration determine rotation of plane polarized light? - Correct Answers ✅No A chiral molecule's mirror image has the _______ absolute configuration - Correct Answers ✅Same What are the conditions of relative configuration? - Correct Answers ✅The two atoms in question must differ in the attachment of only one substituent, and the remaining substituents must be oriented identically relative to the Carbon. MCAT Organic Chemistry Exam Review Question with latest Solution 2024 a Cis isomer has lower possible permutations to form a crystal lattice relative to a Trans isomer, Cis isomers do not form crystals as readily. Higher order alkanes can be differentiated via substituent by the E-Z method. Elaborate. - Correct Answers ✅One were to prioritize the substituents on a Carbon. Then, if one were to note that the higher priority substituent exists on opposite sides, it gets the E label (Entgegen: German for Opposite). If the higher priority substituents are on the same side, it gets the Z label (Zusamen: German for Together) What is a meso compound? - Correct Answers ✅Chiral centers that offset one another due to symmetry. The net result is an optically inactive compound. In essence, meso compounds are actually a chiral. They can be identified by finding a plane of symmetry that divides the compound into two mirror images. What is the formula for maximum number of optically active isomers in a single compound? - Correct Answers ✅2^n, where n is the number of chiral centers. How many functional groups are methyl, primary, secondary, and tertiary alkyl groups connected to, respectively? - Correct Answers ✅0, 1, 2, and 3, respectively. MCAT Organic Chemistry Exam Review Question with latest Solution 2024 List some physical properties of alkanes. - Correct Answers ✅They have low densities. The more molecular weight an alkane has (more Carbon chains), the higher its boiling point due to intermolecular London Dispersion forces. Branching decreases the boiling points because the surface area of the molecule is lowered, and the molecule cannot form a more relatively polar transient dipole. Unbranches alkanes also exhibit an increase in melting point in molecular weight, but not as predictable as the boiling point of alkanes. What is ring strain? - Correct Answers ✅The strain caused by a cycloalkane deviating from the optimal SP3 109.5 degree angle. Ring strain is usually alleviated by the movement of certain bonds away from a flat three dimensional plane. List the relative stabilities of cyclohexane conformers when undergoing a ring flip. - Correct Answers ✅Chair (low) Half Chair (highest) Twist (lower than Half Chair) Boat (higher than twist but lower than Half Chair) Twist of the other side Half chair of the other side Chair of the other side <--- Ring flip done MCAT Organic Chemistry Exam Review Question with latest Solution 2024 When a cyclohexane ring flips conformation, what happens to the equatorial and axial Hydrogens? - Correct Answers ✅They trade conformations. Axials become equatorials, and equatorials become axials. Where are cyclohexane substituents more energetically favored? - Correct Answers ✅At the equatorial position. What is a combustion reaction? - Correct Answers ✅The mixing of alkanes (and similar oxygen containing "CH" groups) with molecular oxygen and an activation energy to produce Carbon Dioxide, Water, and large quantities of heat. Heat of Combustion - Correct Answers ✅Change in enthalpy of a combustion reaction. High heats of combustion means that a molecule needed a large amount of energy to override its intrinsic energy, meaning it contained a large amount of energy. This large amount of energy implies that it relatively unstable. Therefore heats of combustions can be used to compare relative stabilities of compounds. Note the difference between molar heat of combustion that determines if the group were to combust by itself, and the "per CH2" heat of combustion, which includes factors such as ring strain and steric hindrance. Free radical reactions with Alkanes are possible with: - Correct Answers ✅All the Halogens, except I (so F, Cl, Br, but NOT I) can react in the MCAT Organic Chemistry Exam Review Question with latest Solution 2024 What is an alkene? - Correct Answers ✅A Carbon chain with a Carbon- Carbon double bond Are alkenes more acidic than alkanes? Why? - Correct Answers ✅Yes. Because alkenes have double bonds that can stabilize their conjugate bases. The double bond is longer than the single bond of an alkane, and more negative in charge than the single bond of an alkane. This large surface area of negative charge makes alkenes attractive to electrophiles. What is the rule for thermodynamic stability of alkenes? - Correct Answers ✅The more highly substituted an alkene, the more thermodynamically stable. Why is it that more stable alkenes are more reactive when reacted with an electrophile? - Correct Answers ✅Because when an alkene reacts with an electrophile, an intermediate Carbocation forms. This Carbocation is stabilized when there are more alkyl groups to donate their electrons to the Carbocation. List some physical properties of alkenes. - Correct Answers ✅Alkenes exhibit an increase in boiling point due to stronger London Dispersion forces. Branching decreases boiling point due to a lower surface area, which creates a less polarized dipole, lowering the effective energy MCAT Organic Chemistry Exam Review Question with latest Solution 2024 needed to overcome the alkene to separate it to a gaseous phase. Alkenes are slightly soluble in water due to the double bond (acidity implies slight polarity, which implies slight solubility) From the behavior of alkenes, predict the solubility of alkynes. - Correct Answers ✅Alkynes should be slightly more polar, and thus slightly more soluble in water than alkenes. What is the product for dehydration of an alcohol? - Correct Answers ✅An Alkene What is the mechanism for E1 reaction of an alcohol? - Correct Answers ✅The acid protonates the hydroxyl group on the alcohol, making water, which is a good leaving group. Water takes all the electrons of the water-Carbon bond and leaves, leaving behind a Carbocation (this is the slowest, rate determining step). The Carbocation may or may not rearrange to its most stable form. Finally, a water deprotonates a Carbon adjacent to the Carbocation, and a double bond between the two parties forms. Define Saytzeff's Rule - Correct Answers ✅The major product of elimination will be the most substituted alkene. Dehydrahalogenation produces what? - Correct Answers ✅An alkene. MCAT Organic Chemistry Exam Review Question with latest Solution 2024 With respect to base used, what is the difference between E1 and E2 mechanisms? - Correct Answers ✅E1 uses a weak base, E2 uses a strong bulkier base. What is the mechanism of an E1 dehydrohalogenation reaction? - Correct Answers ✅First the halogen drops off, leaving behind a Carbocation. Then hydrogen is removed by a weak base. The extra electron pair left behind the hydrogen is "shared" with the Carbocation, resulting in a double bond and an alkene. What is the mechanism of an E2 dehydrohalogenation reaction? - Correct Answers ✅The strong base removes a proton from the Carbon next to the halogen containing Carbon, creating a carbocation. The halogen drops off as well, all in one step. The extra electron pair is shared with the Carbocation, resulting in a double bond and an alkene. What does catalytic hydrogenation due to an alkene? List the parties that take part in the process. - Correct Answers ✅An alkene is converted to an alkene. Hydrogen gas is supplied to form the saturated hydrocarbon. A heterogeneous catalyst (usually metal shavings of Nickel, Palladium, or Platinum) serves as a catalyst. Syn-Addition adds addition of a substituent where? This results in what type of geometric alkane? - Correct Answers ✅One the same side of two adjacent Carbons. This produces a cis alkane (the hydrogens are added on the SAME side). MCAT Organic Chemistry Exam Review Question with latest Solution 2024 Hot concentrated acid- dehydrates an alcohol to form an alkene In organometallic products, who likes to gain electrons? Who likes to lose electrons? - Correct Answers ✅In organometallic products, the metal likes to lose electrons to take on a partial or full positive charge, while the Carbon likes to gain electrons to gain a partial or full negative charge. What is the product of the oxymercuration/demurcuration reaction? - Correct Answers ✅An alcohol from an alkene. What is the mechanism of the oxymercuration/demercuration reaction? - Correct Answers ✅A mercury reagent partially disassociates to Hg(OAc)+. Then the Hg(OAc)+ acts as an electrophile and attacks the alkene to form a mercurinium ion. Then water attacks the mercurinium ion to form an organomercurial alcohol in an anti-addition (addition on opposite sites) reaction. The mercury is then removed via demurcuration with the addition of a reducing agent and a base. What happens if an alcohol is used instead of water in the oxymercuration/demercuration reaction? - Correct Answers ✅An ether is produced instead of an alcohol. MCAT Organic Chemistry Exam Review Question with latest Solution 2024 What is produced in the hydroboration reaction? What is the type of reaction? - Correct Answers ✅An alcohol from an alkene. Anti- Markovnikov, and syn-addition. It's an Anti-Markovnikov because it takes place in the presence of peroxides. Describe halogenation of an alkene? - Correct Answers ✅Br2 and Cl2 can add to alkenes via anti-addition to form vic-dihalides (two halogens connected to adjacent Carbons). What happens when halogenation takes place with water? - Correct Answers ✅A halohydrin is formed. In the second step, a hydroxyl group is added instead of a halide. A halohydrine is a hydroxyl group and a halogen attached to adjacent Carbons. True or false, Benzene undergoes addition, not substitution. - Correct Answers ✅False, Benzene undergoes substitution, not addition. Addition would disrupt the resonance or the compound, making it no longer be aromatic. True or false, Benzene is flat and is stabilized by resonance, making the rings exhibit partial double bond character. - Correct Answers ✅True. What do electron withdrawing groups do to the ring? Where does it direct constituents if it's in the R group? - Correct Answers ✅Electron MCAT Organic Chemistry Exam Review Question with latest Solution 2024 withdrawing groups deactivate (make less reactive) the benzene ring. It directs in the meta position. What do electron donating groups do to the ring? Where does it direct constituents if it's in the R group? - Correct Answers ✅Electron donating groups active (make more activate) the benzene ring. It is an ortho-para director. Halogens are an exception to the Benzene directing rule. What is the exception? - Correct Answers ✅It is an electron withdrawing group, deactivate the ring, but it directs to the ortho-para position. Is hydrogen electron withdrawing or electron donating? - Correct Answers ✅Neither. For the MCAT, is Benzene electron withdrawing or electron donating? - Correct Answers ✅An electron withdrawing deactivator. What are the names of Benzene compounds with OH, NH2, CH3, COOH, and NO2 respectively? - Correct Answers ✅Phenol, Aniline, Toulene, Benzoic Acid, and Nitrobenzene, respectively. A substitution reaction occurs when a functional group does what? - Correct Answers ✅Replaces another functional group. MCAT Organic Chemistry Exam Review Question with latest Solution 2024 5. SN2 does not react with a sterically hindered substrate (requires methyl, primary or secondary substrate. SN1 requires tertiary or secondary substrate (for carbocation stability). 6. SN1 may rearrange the Carbon skeleton, but SN2 never rearranges the Carbon skeleton. SN2 inverts the stereochemistry of the compound? What's the catch? - Correct Answers ✅If the Carbon is chiral, the relative configuration would be changed 100%, but the relative configuration may or may not change. What happens if the base in the SN2 reaction is too strong? - Correct Answers ✅An E2 reaction might occur, abstracting a base and a potential halogen leaves, forming a double bond. What factors affect nucleophilicty? - Correct Answers ✅Nucleophilicity increases with polarizability, and negative charge. Electronegativity increases nucleophilicity because the nucleophile is less willing to donate its electrons to catalyze the formation of the new compound. What factors make good leaving groups? - Correct Answers ✅Weak bases, polarizability, and electron withdrawing groups make good leave groups. The leaving group is always more stable than the nucleophile, MCAT Organic Chemistry Exam Review Question with latest Solution 2024 otherwise there wouldn't be an incentive for the SN1 and SN2 reactions to occur. How do polar protic solvents affect the SN1 and SN2 reactions? - Correct Answers ✅They stabilize the carbocation and nucleophile (they can Hydrogen bond), speeding up the requirements for the SN1 reaction. However, this slows down the SN2 reaction because the SN2 reaction requires an erratic high energy collision. How does a polar aprotic solvent affect the SN1 and SN2 reactions? - Correct Answers ✅The opposite of the polar protic solvents. It speeds up the SN2 reactions, but slows down the SN1 reaction. What's special about solvolysis? - Correct Answers ✅When the solvent acts as the nucleophile. What are the physical properties of alcohols? - Correct Answers ✅Same trend as alkanes, boiling point increases with molecular weight, and decreases with branching. Melting point increases with molecular weight. However, their values are higher than alkanes due to hydrogen bonding. This makes alcohols more soluble than alkanes. Rank the alcohols from most acidic to least acidic? Why? - Correct Answers ✅Alcohols ranked from most acidic to least acidic is methyl, primary, secondary, and tertiary. As you add more R groups, they MCAT Organic Chemistry Exam Review Question with latest Solution 2024 donate electrons to the central carbon when the alcohol is deprotonated. This "cluster" of negative charge makes the conjugate base very unstable, giving a lower thermodynamic incentive for the alcohol to react as an acid. Methyl alcohols are saturated with Hydrogens, which have a lower electronegativity than Carbon, meaning only the alcohol Carbon can direct negative charge. Since the Hydrogens do not act via the inductive effect, the influence of "more negative charge" is non-existent, meaning a more relatively stable conjugate base, and thus stronger acid. What is the mechanism for Grignard Synthesis of an alcohol? - Correct Answers ✅The organometallic compound disassociates to a positive metal halogen, and a negative R group. The double bond of a Carbonyl dissolves to a single bond, leaving a partial positive charge on the Carbon and a partial negative charge on the Oxygen. The negative R group acts as a nucleophile and attacks the partial positive of the Carbonyl Carbon. After an acid bath, the negative Oxygen is protonated, forming an alcohol. The hydroxyl group from a dissociated water molecule adds to the metallic halogen ion, forming a halo- metallic hydroxide. Grignard's Reagent is made in what type of functional group and is incompatible with what relative acidities? - Correct Answers ✅Grignard's Reagent is made in ether, and is incompatible with water and acids stronger with water. MCAT Organic Chemistry Exam Review Question with latest Solution 2024 What happens when you oxidize a tertiary alcohol? - Correct Answers ✅You cannot oxidize a tertiary alcohol. What happens when an alcohol reacts with a hydrogen halide? What is the mechanism? - Correct Answers ✅The hydrogen halide protonates the hydroxyl group on the alcohol, producing the good leaving group, water (an alkyl group attached to water). Then the halide ion attacks the water bonded alkyl, ejecting the water and producing an alkyl halides. What is the exception to ether reactivity? - Correct Answers ✅Epoxides. Can an ether hydrogen bond with itself? Can it still hydrogen bond? - Correct Answers ✅No, an ether cannot hydrogen bond with itself, but it CAN hydrogen with a hydrogen attached to a F, N, or O atom. Are ethers water soluble? Are ethers better organic solvents than alcohols? - Correct Answers ✅Yes, ethers are slightly soluble in water (similar to alcohols of the same molecular weight). Yes, ethers are pretty decent organic solvents because no hydrogen bonds need to be broken by an organic compound, like they would need to be for an alcohol. MCAT Organic Chemistry Exam Review Question with latest Solution 2024 What is the main reaction that ethers undergo? - Correct Answers ✅Ethers are cleaved by the halo-acids HI and HBr to form a corresponding alcohol. The Oxygen of an ether takes the electrons of an R group, forming a positively charged R group and a negatively charged alkoxyl group. The strong acids disassociate into a proton or a Bromine. The proton attaches to the alkoxyl group to form an ROH. The Bromine attaches to the positively charge R group for form an alkyl halide. What are epoxides, and why are they so reactive? - Correct Answers ✅Epoxides are reactive because the three membred cyclic ethers have angle strain created by the small ring, making the epoxide possesses a lot of energy. What are some of the epoxide reactions? - Correct Answers ✅Epoxide + acid ----> diols via anti-additions Epoxides also likes to get protonated to form alcohols. This happens when the Oxygen rips the electrons away from one of the cyclic Carbons, leaving a positive Carbon. Epoxide + ROH ---> C-C with a vic hydroxyl and alkoxy Epoxide + HX ---> C-C with a vix hydroxyl and halide MCAT Organic Chemistry Exam Review Question with latest Solution 2024 Epoxide + (RO-) ---> C-C with a vic negatively charged Oxygen and alkoxy What are the two things that make Carbonyls susceptible to nucleophilic attack? - Correct Answers ✅Its planar stereochemistry means that it is flat in three dimensional space and can be attacked from many ends. The partial positive charge on the Carbon (from Oxygen taking the charge density from Carbon because Oxygen is more electronegative) also means that it can be attacked by a nucleophile. List some physical properties of aldehydes and ketones? - Correct Answers ✅Due to the Carbonyl double bond, aldehydes and ketones are more polar, and thus are more water soluble. The charge polarity means that a transient dipole is formed, and its boiling point us higher for alkanes and alkenes of similar weight. Due to steric hindrance, aldehydes and ketones cannot hydrogen bond with one another, but can hydrogen bond with water and other solvents that can hydrogen bond. Aldehydes and Ketones under reactions via which two pathways? - Correct Answers ✅Either by acting as a Bronsted-Lowry base and donating an acidic alpha hydrogen, or as a substrate in nucleophilic addition. MCAT Organic Chemistry Exam Review Question with latest Solution 2024 What is the significance of a "blocking group"? - Correct Answers ✅Blocking groups are formed from acetals and ketals that are unreactive towards bases. Think about it like this. Bronsted-Lowry bases give protons, which make them reducing agents (they reduce other products). Well, an acetal or ketal already has the maximum amount of Hydrogens it can react with, meaning it won't take the Hydrogen and thus will not react with the base. Aldehydes or Ketones can be temporarily changed to an acetal or ketal to prevent nucleophilic attack by a base. What happens when aldeydes or ketones are dissolved in aqueous solutions? - Correct Answers ✅Aldehyde + Water reaction. The Carbonyl Oxygen takes two electrons, reducing the double bond to a single bond. Now the Water drops off a Hydrogen, which attaches to the Oxygen. The remaining hydroxyl group then attaches to the single bond made from the loss of the Carbonyl double bond. This creates a hydrate (geminal diol). The same mechanism works with a ketone. What are the possible types of Aldol reactions? - Correct Answers ✅Aldehyde-Aldehyde, Ketone-Ketone, or Aldehyde-Ketone. MCAT Organic Chemistry Exam Review Question with latest Solution 2024 Describe the mechanism that occurs when a methyl ketone is reacted with a base and a halide. - Correct Answers ✅The reaction results adding 3 Bases (hydroxides), 3 halides (X2) and a methyl ketone. The halide ion displaces the Hydrogen on the methyl group of the methyl ketone such that the 3 Hydrogens are displaced by 3 Halogens atoms. This results in a degredation from 3 X2 to 3 X- and 3 H2O (the 3 Hydrogens from the Methyl Ketone transfer to the Hydroxide, making water). Water drops a Hydrogen, the Carbonyl Oxygen takes two electrons to make a single bond and have a negative charge, and hydroxyl group now attaches to the carbocation. A new double bond forms from the Oxygen, displacing the carbohalide. The hydroxyl group drops off a Hydrogen, which attaches to the haloform, and a Carboxylate ion and Haloform forms. What does the Wittig Reaction do? - Correct Answers ✅Converts a ketone to an alkene. Describe the Wittig reaction. - Correct Answers ✅A phosphorus ylide (a ylide is an overall neutral molecule, which is a phoshorus bonded with three benzene rings and a carboanion) reacts with a ketone. The ketone undergoes nucleophilic addition, forming an unstable Betaine. This Betaine breaks apart, producing a triphenylphosphine oxide and an alkene. The Wittig reaction produces both cis and trans isomers. Beta carbons undergo nucleophilic addition directly, this is called? - Correct Answers ✅Conjugate addition. MCAT Organic Chemistry Exam Review Question with latest Solution 2024 How is a carboxylic acid salt named? How is it structured? - Correct Answers ✅It is named by dropping the "ic" or "oic" and replacing it with an ate. For example, a sodium salt of acetic acid is named sodium acetate. The structure is drawn by dropping off the hydroxyl Hydrogen and adding the cation next to the Oxygen. The cation has a positive charge, the Hydrogen-less hydroxyl group has a negative charge, so the two meet via electrostatic attraction. How do Carboxylic acids behave when undergoing nucleophilic reactions? - Correct Answers ✅They like to undergo nucleophilic substitution, because the hydroxyl group easily protonates, and the leaving group water, leaves. This causes part of a reagent or another functional group to take the place water filled in before. This is the definition of a substitution reaction- one functional group replacing another. Why are Carboxylic Acids strong? - Correct Answers ✅Because the conjugate base is stabilized by resonance. The double of the carbonyl group can be shifted to the negative oxygen. Now, instead of a cluster of unstable negative charge, the electrons are delocalized, lowering this cluster of negative charge. What are the implications with respect to physical properties when a Carboxylic Acid forms a dimer? - Correct Answers ✅Because two carboxylic acid molecules can join by Hydrogen bonding (the Hydrogen MCAT Organic Chemistry Exam Review Question with latest Solution 2024 reaction between an ester and an alcohol as the two reactants, and the products are an ester and an alcohol as well. It's just the "OR" groups of the ester and alcohol swap. What is a Beta-Keto acid? - Correct Answers ✅A Carboxylic Acid where the Beta Carbon is also a Carbonyl. What is the product of an acetoacetic ester synthesis reaction? - Correct Answers ✅A ketone What is the mechanism of an acetoacetic ester synthesis? - Correct Answers ✅First an acetoacetic ester reacts with a base, and alpha hydrogens are removed. The resulting enolate (the negatively charged enol ion that results from a carboanion) is alkylated by an alkyl halide (R-X) or a toslylate, making an alkylacetoacetic ester. Then, this alkylacetoacetic (which has a Beta carbonyl) is decarboxylated in the presence of an acid to form the ketone. How are amides formed? - Correct Answers ✅When an amine acts as a nucleophile for a carboxylic acid or its derivatives, and substitutes at the hydroxyl group (or the derivative group). Label these in terms of increasing acidity: acyl chloride, carboxilic acid, ester, amide, acid anhydride. - Correct Answers ✅Acyl chlroide > acid anhydride > carboxylic acid > ester > amide. MCAT Organic Chemistry Exam Review Question with latest Solution 2024 What are the three important considerations when dealing with Nitrogen containing compounds on the MCAT? - Correct Answers ✅1) They can form 4 bonds and take on a positive charge 2) They can use their lone pair of electrons to attack a positive charge and act as nucleophiles 3) They can DONATE their pair of electrons as a Lewis base (different than #2) Ammonia and amines act as strong bases or weak bases? - Correct Answers ✅Weak bases. What would an electron withdrawing substituent due to the basicity of an amine? - Correct Answers ✅It would decrease it, because electron withdrawing groups reduce the charge density. Now, the amine cannot donate its electrons as strongly (because it's charge density was weakened). Because a Lewis base is defined as the propensity to donate electrons, and this ability is weakened, basicity is decreased. What would an electron donating substituent due to the basicity of an amine? What's the catch? - Correct Answers ✅Electron donating groups give electrons to the Nitrogen, increasing its charge density and propensity to donate electrons, hence increasing its Lewis basicity. MCAT Organic Chemistry Exam Review Question with latest Solution 2024 HOWEVER, too many electron withdrawing groups can contribute to steric hindrance. Because alkyl groups (R groups) are electron donating, the basicity of amines is given as: Secondary > Primary > Ammonia (tertiary and quaternary are too sterically hindered) What would adding a benzene ring to an amine due to its basicity? - Correct Answers ✅It would weaken it because the lone pair of electrons on the Nitrogen can be delocalized around the ring, decreasing its tendency to donate. Electron withdrawing groups on Benzene further decrease basicity. The notion that a Nitrogen donates its electrons means what with respect to carbocations? - Correct Answers ✅It means that Nitrogens can donate their electrons to stabilize carbocations if they are part of the same molecule. Which amines can hydrogen bond with one another? - Correct Answers ✅Ammonia (a 0th order amine), primary, and secondary can hydrogen bond with one another. MCAT Organic Chemistry Exam Review Question with latest Solution 2024 What is the saponification? - Correct Answers ✅The cleavage of triacyglycerols via NaOH. Amphipathic refers to what properties of a fatty acid? - Correct Answers ✅Exhibiting hydrophilic and hydrophobic ends. Fatty acids are amphipathic because the carboxylic head is hydrophilic, while the alkane tails are hydrophobic. Because the carbon chain predominates, however, fatty acids are nonpolar. Fatty acids can be used as an intermediate to what biological process (think energy)? - Correct Answers ✅The Krebs cycle, where they enter TWO Carbons at a time. Amino acids make what? They are strung by what type of bonds? - Correct Answers ✅Proteins. Peptide bonds. Hence, why a protein is called a "polypeptide" (many peptides). How is a peptide bond formed? - Correct Answers ✅Via dehydration reactions. The carboxyl group loses its OH, the amine group loses an H. The net result is a water molecule. Now, the two ends meet. Hydrolysis reverses this process (uses the OH to reform the carboxyl end of an amino acid, and uses H to reform the amino end of the amino acid, resulting in two amino acids as opposed to a peptide). MCAT Organic Chemistry Exam Review Question with latest Solution 2024 Alpha amino acids refer to what type of amino acids? - Correct Answers ✅Those used by the human body. What are the implications of Nitrogen being able to take on four bonds and the Oxygen being able to exist as a negative charge with respect to structure of the polypeptide? - Correct Answers ✅The excess electrons of a negatively charged Oxygen can exist in resonance with the Nitrogen. This creates a double bond character that prevents free rotation, which has implications in secondary and tertiary structure. How many total amino acids are there that most organisms use? How many are essential? What does essential mean? - Correct Answers ✅There are 20 amino acids used by most organisms. Ten are essential. Essential amino acids are ones that cannot be synthesized by the body and must be ingested. An amino acid has the following structure: A central Carbon attached to a Hydrogen. One side, has a carboxyl end, the other has an amino end. Since Carbon can take on one more bond, what is this variable bond called? What are its implications? - Correct Answers ✅This is called a side chain, and it is important because the properties of the side chain MCAT Organic Chemistry Exam Review Question with latest Solution 2024 influence the properties of the amino acids. An electron withdrawing or donating side chain can make the amino acid behave differently. List the basic amino acids. - Correct Answers ✅Histidine Lysine Arginine. List the acidic amino acids. - Correct Answers ✅Glutamic Acid Aspartic Acid List the polar amino acids. - Correct Answers ✅Serine Threonine Cysteine Tyrosine Glutamine Aspargine List the nonpolar amino acids - Correct Answers ✅Leucine Isoleucine Valine Alanine MCAT Organic Chemistry Exam Review Question with latest Solution 2024 How do you read a Fischer projection? - Correct Answers ✅The vertical lines are the main chain of Carbons, and the horizontal chains go OUT of the main chain. How do you determine whether or not a carbohydrate is labeled "D" or "L"? - Correct Answers ✅In a Fischer projection, locate the highest number chiral Carbon. If that highest number chiral Carbon's has a hydroxyl group that points RIGHT, it is D. If it points LEFT, it is L. How can the highest number chiral Carbon's hydroxyl group behave with respect to reactivity? How do I locate the anomeric carbon now? - Correct Answers ✅It can serve as a nucleophile and attack the Carbonyl Carbon, forming a ring. The anomeric Carbon, which is Carbon 1, is identified by being the only Carbon bonded to two Oxygens. How does one use the ring number to name a carbohydate? - Correct Answers ✅Using the ending "ose". Five membered rings are called "furanose". Glucose, a six membered ring is a "pyranose" What are acetal sugars called? - Correct Answers ✅Glycosides. The names of such sugars end in "oside". Can Tollen's reagent reduce glycosides? - Correct Answers ✅No, because the acetal groups of glycosides act as "blocking agents", MCAT Organic Chemistry Exam Review Question with latest Solution 2024 preventing the reaction with bases. If Tollen's reagent is reducing something, it is gaining "H2" or "2 Protons" hence making it a base. Acetals block reactions with bases. What is the group attached to the anomeric carbon of a glycoside called? - Correct Answers ✅An aglycone. List the relevant carbohydrate information of: Sucrose. - Correct Answers ✅1,1' glycosidic linkage between glucose and fructose. List the relevant carbohydrate information of: Maltose. - Correct Answers ✅Alpha-1,4' glycosidic linkage between 2 glucose molecules. What is a glycosidic linkage? - Correct Answers ✅Covalent bonds between two Carbons. What is the alpha-beta distinction in carbohydrates? - Correct Answers ✅Alpha groups have aglycones that face DOWN with respect to the plane of the anomeric Carbon. Beta groups have aglycones that face UP with respect to the plane of the anomeric Carbon. List the relevant carbohydrate information of: Lactose. - Correct Answers ✅Beta-1,4' galactosidic linkage between galactose and glucose. MCAT Organic Chemistry Exam Review Question with latest Solution 2024 List the relevant carbohydrate information of: Cellulose. - Correct Answers ✅Beta-1,4' glycosidic linkage between a chain of glucose molecules. List the relevant carbohydrate information of: Amylose. - Correct Answers ✅Alpha-1,4' glycosidic linkage between a chain of a glucose molecules. List the relevant carbohydrate information of: Amylopectin. - Correct Answers ✅Alpha-1,4' glycosidic linkage between a chain of a glucose molecules WITH an alpha-1,6' glycosidic linkage forming the branches. List the relevant carbohydrate information of: Glycogen. - Correct Answers ✅Alpha-1,4' glycosidic linkages between a branched chain of glucose molecules with alpha-1,6' glycosidic linkages forming the branches. What are the differences between amylopectin and glycogen if both of them have alpha-1,4' glycosidic linkages between glucose molecules and alpha-1,6' linkages for branches? - Correct Answers ✅Amylopectin is found in plants, while glycogen is found in animals. Glycogen is longer than amylopectin. MCAT Organic Chemistry Exam Review Question with latest Solution 2024 In an NMR plot, how does magnetic field strength vary? - Correct Answers ✅On an NMR plot, the field strength is measured in parts per million (PPM) that DECREASES from left to right. However, despite the PPM NUMBER decreasing from left to right, the magnetic field strength actually INCREASES from left to right. Left is called "downfield" and up is called "upfield". Why is there a peak at 0 PPM on an NMR plot? - Correct Answers ✅This is the energy of a reference compound that calibrates the NMR device. Each peak represents what on an NMR plot? - Correct Answers ✅Hydrogen equivalent Hydrogens. What is splitting on an NMR plot? - Correct Answers ✅It is created by "neighboring" Hydrogens on a plot. If a Hydrogen is "enantiotropic" what does this mean? - Correct Answers ✅It means that the Hydrogens are indistinguishable by means of their positions relative to a compound. Enantiotropic Hydrogens have the same chemical shift (difference between resonance frequency and frequency of a Hydrogen- pretty much how far out it is on the X-axis) MCAT Organic Chemistry Exam Review Question with latest Solution 2024 If an NMR plot has a peak of Hydrogens clustered together, are those Hydrogens necessarily bonded to the same central atom? - Correct Answers ✅No, the peaks represent stereochemically similar Hydrogens. The area under an NMR peak represents? - Correct Answers ✅It is a proportionality value related to the number of Hydrogens represented by that peak. Do tall peaks mean greater areas? - Correct Answers ✅Not always. The peak can be thin. Therefore, DO NOT assume the tallest peak means that that group has the most stereochemical Hydrogens. What is an integral trace? - Correct Answers ✅A line drawn above peaks that rises each time the peak rises. It gives the relative number of Hydrogens between one peak and another. IT DOES NOT give the exact number of Hydrogens, only a ratio. So if one peak is TWICE as high as the other, that means the Hydrogens of the taller peak are DOUBLE in number than the Hydrogens of the lower peak. What exactly causes splitting? - Correct Answers ✅Neighboring Hydrogens that differ in chemical energy. So, the splitting is caused by Hydrogens that aren't chemically equivalent. MCAT Organic Chemistry Exam Review Question with latest Solution 2024 What is the relationship between the number of peaks and the number of neighboring Hydrogens that are not chemically equivalent? - Correct Answers ✅The number of peaks due to splitting for a group of chemically equivalent Hydrogens is n+1. Where n is the number of NON- CHEMICALLY EQUIVALENT neighboring Hydrogens. What will an electron withdrawing group do the chemical shift of a compound in an NMR plot? - Correct Answers ✅It will withdraw electron density, lowering shielding. Since a Hydrogen isn't shielded, it takes a weaker magnetic field to make it absorb energy (it doesn't have to overcome the energy of the "guardian" electrons). Thus, it shifts the chemical shift to the left (remember leftward means weaker magnetic fields because the magnetic field increases from left to right). What will an electron donating group do the chemical shift of a compound in an NMR plot? - Correct Answers ✅It will donate electrons, and contribute to electron density, INCREASING shielding. Since a Hydrogen is shielded more extensively, it takes a stronger magnetic field to make it absorb energy (it now has to overcome the energy of the "guardian" electrons). Thus, it shifts the chemical shift to the right (remember rightward means stronger magnetic fields because the magnetic field increases from left to right). Aldehyde protons have a very distinct shift where on an NMR plot? - Correct Answers ✅9.5 PPM MCAT Organic Chemistry Exam Review Question with latest Solution 2024 What are the rules for UV Spectroscoy analysis? - Correct Answers ✅UV light starts at ~200nm naturally. Each compound then absorbs UV at a starting point a little greater than 200nm. For each conjugated double bond past the first conjugated double bond, there is an increases the compound's absorbance wavelength by ~30-40nm, and each alkyl substituent group attached to an atom increases the absorbance wavelength by ~5nm. Isolated double bonds (double bonds not separated by one single bond) have no effect on the absorption wavelength. How is the color of an object found via UV spectroscopy? - Correct Answers ✅It's maximum absorbance is found within the visible light region. The color corresponding to the absorbance wavelength is, as the name implies, ABSORBED by the object and not the object's color. The wavelength that you see is the COMPLEMENTARY color of the the absorbance wavelength (the complementary color represents the wavelength reflected by the object). You probably (99%) don't need know the complementary colors for the MCAT, but if you were curious: Complementary colors: Red-Green Blue-Orange Purple-Yellow MCAT Organic Chemistry Exam Review Question with latest Solution 2024 What does mass spectrometry give? What about high resolution mass spectrometry? - Correct Answers ✅Mass spectrometry gives the molecular weight of a compound. High resolution mass spectrometry gives the molecular formula and molecular weight of a compound. How does mass spectrometry work? - Correct Answers ✅Molecules of a sample are bombarded with electrons, causing them to break apart and ionize. The largest ion is called the "molecular ion" and is equal to the original molecule, but with one positive charge. These ions are then subjected to the force of a magnetic field, which causes them to accelerate around a curved path (F=qvb of a molecule equal to F = mv^2/r of circular motion). The radius of curvature depends on the mass to charge ratio of the ion. The magnetic field, and thus paths, are varied, and certain ions can move through a filter, which passes through a computer and is recorded. A plot of abundance against mass to charge is plotted. Abundance is how tall one peak is relative to another peak. What is the largest peak in a mass spectrometer called? - Correct Answers ✅The base peak. What is the peak made by the molecular ions ion a mass spectrometer called? - Correct Answers ✅The parent peak. How does chromatography work? - Correct Answers ✅A mixture is separated by being passed over a matrix that adsorbs (adsorbance is MCAT Organic Chemistry Exam Review Question with latest Solution 2024 different than absorbance. Absorbance is internal uptake, adsorbance is external bonding on a surface) different compounds with different affinities based on polarity. Polarity is a good measure because it affects how likely a part of a compound adheres to the matrix. What is the relationship between polarity and separation in chromatography paper? - Correct Answers ✅Because the paper, cellulose, is polar, polar substances adhere to the paper (like dissolves like) and are slower to separate away than nonpolar substances, which repel. In the end, the different separation points can distinguish arts of a mixture. What is column chromatography? - Correct Answers ✅Column chromatography is when a solution that contains the mixture under analysis is dripped on the column containing the solid phase (the intact resolving matrix). Usually the solid phase is glass. Glass, which is silicon dioxide and has a net dipole moment, is polar. Therefore, polar parts of a compound adhere and move slower than nonpolar parts. What is paper chromatography? - Correct Answers ✅The sample to be separated is spotted onto a piece of paper. One end of this paper is then placed into a solvent. The solvent, which is usually polar, moves up the paper through capillary action and dissolves the sample as it runs across the paper. More polar components move slower than nonpolar components. This establishes different colors that represent the different components of the sample. The most polar part remains at the