23.14 23.8 HOFMANN ELIMINATION OF QUATERNARY A12 21 Continue the sequence of reactions in Eqs. 23.16a-c to show how trimethylammonium iocin Eq. 23.15.23,22 Outline a preparation of each of the following from an amine and an acid chloride.(a) N-phenylbenzamide(b) N-benzyl-N-ethylpropanamide23.8HOFMANN ELIMINATION OF QUATERNARYAMMONIUM HYDROXIDESThe previous section discussed ways to make carbon-nitrogen bonds. In these reactianines react as nucleophiles. The subject of this section is an elimination reaction useoreak carbon-nitrogen bonds. In this reaction, which involves quaternary ammonium hyaues (R,N* ¯OH) as starting materials, amines act as leaving groups.When a quaternary ammonium hydroxide is heated, a B-elimination reaction t.e to give an alkene, which distills from the reaction mixture.CH2 NME3NMe,-CH, + H-—ОНheattrimethylamineH.FHO-a quaternary ammoniumhydroxidemethylenecyclohexane(74% yield) + HI (23.21)Eqs. 23.19 and 23.21) is called exhaustive methylation.imines and enamines, respectively (Sec. 19.11). In the presence of a reducing agent, iminesWhen primary and secondary amines react with either aldehydes or ketones, they formConversion of an amine into a quaternary ammonium salt with excess methyl iodide (as inCH;CH3sec-butyltrimethylammoniumsec-butylmethylamineiodideB. Reductive Aminationand enamines are reduced to amines.NEtNHE.-H2OH2, Pt30 psiELOHE:NH2 + H3C-C-CH3H3C-C-CH3H;C-CH-CH3(23.22)an imine(not isolated)acetoneethylisopropylamineReduction of the C=N double bond is analogous to reduction of the C=0 double bond(Sec. 19.8). Notice that te imine or enamine does not have to be isolated, but is reducedwithin the reaction mixture as it forms. Because imines and enamines are reduced morerapidly than carbonyl compounds, reduction of the carbonyl compound is not a competingreaction.PROBLEM23.14 Provide a reaction mechanism for step 1, formation of the imine, in Eq. 23.22 (Hint: Refer to Sec. 19.11A).

When an amine reacts with ketone, imine is formed as follows:

ducing agent, imines NEt NHẸt -H2O EINH, + HC—C—СH, H3C-C-CH3 H, Pt 30 psi ELOH H,C-CH-CH3 (23.22) an imine (not isolated) acetone ethylisopropylamine Reduction of the C=N double bond is analogous to reduction of the C=0 double bond (Sec. 19.8). Notice that thhe imine or enamine does not have to be isolated, but is reduced within the reaction mixture as it forms. Because imines and enamines are reduced more rapidly than carbonyl compounds, reduction of the carbonyl compound is not a competing reaction. PROBLEM 25.14 Provide a reaction mechanism for step 1, formation of the imine, in Eq. 23.22 (Hint: Refer to Sec. 19.11A).

ducing agent, imines NEt NHẸt -H2O EINH, + HC—C—СH, H3C-C-CH3 H, Pt 30 psi ELOH H,C-CH-CH3 (23.22) an imine (not isolated) acetone ethylisopropylamine Reduction of the C=N double bond is analogous to reduction of the C=0 double bond (Sec. 19.8). Notice that thhe imine or enamine does not have to be isolated, but is reduced within the reaction mixture as it forms. Because imines and enamines are reduced more rapidly than carbonyl compounds, reduction of the carbonyl compound is not a competing reaction. PROBLEM 25.14 Provide a reaction mechanism for step 1, formation of the imine, in Eq. 23.22 (Hint: Refer to Sec. 19.11A).

Organic Chemistry

8th Edition

ISBN:9781305580350

Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Publisher:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Chapter22: Reactions Of Benzene And Its Derivatives

Section: Chapter Questions

Problem 22.51P

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