Alkene Addition Reactions Cheat Sheet, Cheat Sheet of Organic Chemistry

Download Alkene Addition Reactions Cheat Sheet and more Cheat Sheet Organic Chemistry in PDF only on Docsity! 2) NaBH4, NaOH H2SO4 dilute 1) BH3, THF 2) H2O2, NaOH KMnO4 -OH, cold 1) O3 2) Me2S 1) RCO3H OsO4 Br2 H2O Addition of Hydrogen halide (HX) Hydroboration-Oxidation Oxymercuration Acid-catalyzed hydration Halogenation Halohydrin Formation Hydrogenation Ozonolysis HX HBr ROOR NBS Br Radical Addition of HBr Br2 H2 Pd/C OH OH OH H H OH O O + H OH OH + OH HO OH OH + OH HO HO OH + OH OH Br Br + Br Br HO Br + OH Br Syn Dihydroxylation Syn Dihydroxylation Anti Dihydroxylation OH + X Only HBr works for Anti-Markovnikov addition. The reaction goes through a radical mechanism with syn and anti additions. Allylic Bromination + Br Br + Br 1) Hg(OAc)2 NaHSO3 O + En Epoxide 2) H3O H2O Trans diols - enantiomers (MCPBA) + Enantiomers Simmons–Smith reaction CH2I2 Zn, CuCl H2 C + En Additions to Alkenes The reaction goes through a regioselective formation of a carbocation. This is the Markovnikov's rule stating that the proton binds to the less substituted carbon because by doing so the more substituted/stable carbocation is formed. The halide can attack the carbocation from both faces, thus a mixture of enantiomers is produced. X H X X ++ H 3o carbocation more stable 2o X H X Enantiomers * Notice that an alkene with a chiral center will produce a mixture of diastereomers. Br Br Br Br H H H H + + + NBS is used to brominate the allylic position of the double bond. So, for the regiochemistry of the bromination, you can simply identify the allylic positions and place the bromine there. However, the reaction is not as straightforward! It involves resonance-stabilization of the allylic radicals and other regioisomers are also formed. In addition, the lack of stereochemical control makes predicting all the possible products quite difficult. You can check https://www.chemistrysteps.com/allylic-bromination/ for more details. Acid-catalyzed hydration follows theMarkovnikov's rule. However, rearrangements are possible because of the carbocation intermediates. HOH Dilute H2SO4, H + OHH H Hhydride shift H H H H H2O 2o 3o OH OH expected observed Syn and anti addition. 1) Hg(OAc)2, EtNH2 2) NaBH4 Same product as acid-catalyzed hydration. The main reason for using Oxymercuration is preventing possible rearrangements that happen during acid-catalyzed hydration. The mechanism goes through a three-membered ring which can react with other nucleophiles such as alcohols, amines and thiols. HN Hg + En + En 1) EtNH2 OAc Unlike H2SO4 and Hg(OAc)2, Hydroboration-Oxidation is used for Anti-Markovnikov hydroxylation. Hydroboration is a concerted, syn addition, so the H and OH appear on the same side in the product. For better stereoselectivity, bulky dialkylboranes such as 9-BBN (R2BH general formula) are used. 1) BH3, THF + En H BH2 + En H OH Like for any other exercise, numbering the carbon chain will help a lot! 12 3 4 5 6 1) O3 2) Me2S 1 2 3 4 5 6 O O H The syn dihydroxylation with KMnO4 works only at lowered temperatures . If heat is applied, the double bond is cleaved: KMnO4 warm O O + H O OHOH HO glycol ketone aldehyde-oxidized acid O + ketone An epoxide is a strained three-membered, cyclic ether that can be reacted with many other nucleophile since epoxides are very reactive. Nu OH O + En 1) Nu + En In epoxide opening, the nucleophilic attack generally occurs at the more substituted carbon atom for weak nucleophiles and at the less substituted carbon atom for strong nucleophiles. 2) H2O Stereochemistry is the key in halogenation of a double bond. A three-membered ring intermediate (bridged halonium ion) is formed upon addition of the first halogen and the second one can only add from the opposite side.Thus, trans enantiomers formed by anti addition. Br2 Br Br + En + En Br Br Same mechanism as bromination. Only the bridgedhalonium ion is attacked by the water here. Key point for regiochemistry : the water attacks the more substituted carbon of the ring. Key point for stereochemistry : the Br and OH are trans since H2O attacks from the opposite side. OH Br + En + En Br H2O Other catalysts such as Pt or Ni can also be used for catalytic hydrogenation of alkenes. It is a syn addition. For homogeneous reactions,Wilkinson's catalyst is used instead of metals. It is a stereospecific reaction and depending on the configuration of the alkene, cis or trans product is obtained: There is no stereoselectivity and a maximum number of stereoisomers can be formed. O + OTo predict the structure of starting alkene, connect the two carbons of carbonyl with a double bond: connect 12 3 4 1 2 3 1 2 3 123 4 Rh(Ph3P)3Cl H2 (1 atm) Wilkinson's catalyst Carried out in solution RR CH2I2 Zn, CuCl(Z) Cis R CH2I2 Zn, CuCl RR H2 C (E) Trans R RR H2 C 2) H2O2, NaOH X = F, Cl, Br. I