Final Exam Problems - Organic Chemistry II: Reactivity, Synthesis | CHEM 30B, Exams of Organic Chemistry

Download Final Exam Problems - Organic Chemistry II: Reactivity, Synthesis | CHEM 30B and more Exams Organic Chemistry in PDF only on Docsity! Chem 30B Winter 2004 Final Exam – Part B Page 1 1. (6 points) Above or next to each arrow write the appropriate reagents. CH2OH CO2H CO2CH3 HO 2. (2 points) Circle the molecule with the highest boiling point. H2N NH2 O H2N CH2CH3 O CH3CH2 CH2CH3 O 3. (5 points) Fill in the blanks with the number or phrase (no more than four words) that best completes each sentence: The molecular force that has the greatest influence on your choice in question 2 is __________________________. This force is typically ______________ kcal mol-1. Another, very weak molecular force that also influences the boiling point of this compound is __________________________. 4. (2 points) The solubility of urea in water is best described as (circle one): Highly soluble Moderately soluble Insoluble Cannot be estimated 5. (10 points) For each pair of reactions, write the product of the faster reaction in the box between the reactions. ⇓ Product of faster reaction ⇓ (a) O 1. CH3MgBr 2. H3O+ H O1. CH3MgCl 2. aq. H2SO4 (b) N(CH3)2 O PhNH2 H3O+ CH3O O PhNH2 H3O+ Chem 30B Winter 2004 Final Exam – Part B Page 2 6. (12 points) Suggest a series of reactions to synthesize the following ester. All of the carbon atoms in the target ester must come only from toluene (PhCH3) or bromobenzene (PhBr). (It is not necessary to use both.) You may use any other needed reagents and reasonable reactions. Logical retrosynthesis may earn some partial credit, but is not required. OK to use the Ph abbreviation. O O Synthesis target = Retrosynthesis (optional): Forward direction: 7. (6 points) By now you should be able to figure out mechanisms for some reactions that you have never seen before. Using what you have learned in the past two quarters of organic chemistry, suggest a reasonable mechanism for the following reaction sequence. OO 1. CH3O- 2. CH3I O CH3O OCH3 Chem 30B Winter 2004 Final Exam – Part B Page 5 IR spectrum for problem 11. Detach this page. It will be discarded before grading. Chem 30B Winter 2004 Final Exam – Part B Page 6 Detach this page. It will be discarded before grading. Natural Abundance of Important Isotopes 1H (99.985%), 2H (0.015%) 32S (95.0%), 33S (0.76%), 34S (4.22%) 12C (98.893%), 13C (1.107%) 35Cl (75.77%), 37Cl (24.23%) 14N (99.634%), 15N (0.366%) 79Br (50.69%), 81Br (49.31%) 16O (99.759%), 17O (0.037%), 18O (0.204%) 127I (100%) 19F (100%) Characteristic Infrared Stretching Frequencies Functional Group Bond Stretching, cm-1 Intensity alcohol O-H 3650 – 3590 variable (not H-bonded) alcohol O-H 3600 – 3200 strong, broad (H-bonded) amine, amide N-H 3500 – 3300 medium, often broad alkyne sp C-H 3300 strong aryl, vinyl sp2 C-H 3100 – 3000 variable carboxylic acid O-H 3000 – 2500 strong, broad alkane sp3 C-H 2960 – 2850 strong aldehyde sp2 C-H 2900, 2700 medium, 2 bands nitrile C≡N 2260 – 2220 variable alkyne C≡C 2260 – 2100 variable aromatic overtones 1950 – 1750 weak; usually four humps ester C=O 1750 – 1735 strong aldehyde C=O 1740 – 1720 strong ketone C=O 1750 – 1705 strong carboxylic acid C=O 1725 – 1700 strong aryl ketone C=O 1700 – 1680 strong amide C=O 1690 – 1650 strong α,β – unsaturated ketone C=O 1685 – 1665 strong alkene C=C 1680 – 1620 variable aromatic C=C ≈1600, 1500 - 1450 variable; 1600 often 2 bands Characteristic Proton NMR Chemical Shifts (ppm) RCH3 0.9 RC≡CH 2.5 RCHO, ArCHO 9.5 – 11 RCH2R acyclic 1.3 RNHCH3 2 – 3 RNH2 1 – 3 RCH2R cyclic 1.5 RCH2X (X = Cl, Br, I) 3.5 ArNH2 3 – 5 R3CH 1.5 – 2.0 R OCH3 O ROCH3, 3.8 R N O R H 5 – 9 R R CH3R 1.8 R2C=CH2 5.0 ROH 1 – 5 R CH3 O 2.0 – 2.3 RCH=CR2 5.3 ArOH 4 – 7 ArCH3 2.3 ArH 6.5 – 8 RCO2H 10 – 13