Acid-catalyzed nucleophile addition

Steps 1-3 Acid catalyzed nucleophilic addition of 1 mole of ethanol to the carbonyl group The details of these steps are analogous to the three steps of acid catalyzed hydration in Figure 17 7 The product of these three steps is a hemiacetal... 

Unsaturated Hydrocarbons. Olefins from ethylene through octene have been converted into esters via acid-catalyzed nucleophilic addition. With ethylene and propjiene, only a single ester is produced using acetic acid, ethyl acetate and isopropyl acetate, respectively. With the butylenes, two products are possible j -butyl esters result from 1- and 2-butylenes, whereas tert-huty esters are obtained from isobutjiene. The C5 olefins give rise to three j iC-amyl esters and one /-amyl ester. As the carbon chain is lengthened, the reactivity of the olefin with organic acids increases. 

The step in which the nucleophile attacks the carbonyl carbon is rate-detennining in both base-catalyzed and acid-catalyzed nucleophilic addition. In the base-catalyzed mechanism this is the first step. 

This section reviews recent developments in the chemistry of 4-acetoxy-1,3-diox-anes. Highly selective Lewis acid catalyzed nucleophilic additions are described, including their potential utility in natural product synthesis. 

In contrast, the reaction of acid-catalyzed nucleophilic addition of alcohols to derivatives of AH -imidazol-1 -oxide (219) and (224) leads only to nitronyl nitroxyl (221) and imino nitroxyl (274) radicals (518). 

Unsaturated Hydrocarbons. Olefins from ethylene through octene have been converted into esters via acid-catalyzed nucleophilic addition. 

There are two reaction pathways for addition of neutral and anionic nucleophiles to p-1 (Scheme 39) direct nucleophile addition with rate constant kNu (M 1 s 1) and specific acid-catalyzed nucleophile addition kHNu (M 2 s 1), through the protonated intermediate p-H-l+ with an acidity constant and microscopic rate constants of ks and k- u (Scheme 39) for addition of solvent or nucleophilic anion to form product. Eqs. (2a) and (2b) show the... 

Two pathways are observed for nucleophile addition to 48 in water (Scheme 49) (i) uncatalyzed nucleophile addition to form the oxygen anion 48 that undergoes rapid protonation (ii) specific acid-catalyzed nucleophile addition. The SDIE on the specific acid-catalyzed addition of solvent and bromide anion to 48 are kH/kD = 0.68 and 1.0, respectively, for reactions in 50/50 (v/v) water trifluoroethanol,67 but a smaller SDIE of kH/kD = 0.41 is observed for the specific acid-catalyzed addition of an aqueous solvent to l.52 The larger SDIE for acid-catalyzed addition of Br to 48 is consistent with a concerted reaction mechanism, in which protonation of oxygen and carbon-bromine bond formation occur in a single step with a rate constant kHBr (Scheme 49). 

The following reaction is the acid-catalyzed nucleophilic addition of water across the carbonyl group of acetone. This hydration of a ketone or aldehyde is discussed in Section 18-13. 

The mechanism of imine formation (Key Mechanism 18-5) begins with an acid-catalyzed nucleophilic addition of the amine to the carbonyl group. Attack by the amine, followed by deprotonation of the nitrogen atom, gives an unstable intermediate called a carbinolamine. 

Acid-catalyzed nucleophilic addition to the carbonyl group, and... 

Acid-catalyzed nucleophilic addition of a nitrile to a carbenium ion generated from alcohol (usually tertiary primary alcohols other than benzyl alcohol will not react), yielding an amide. Sanguigni, J.A. and Levine, R., Amides from nitriles and alcohols by the Ritter reaction, J. Med. Chem. 53, 573-574, 1964 Radzicka, A. and Konieczny, M., Studies on the Ritter reaction. I. Synthesis of 3-/5-bartbituryl/-Ipropanesulfonic acids with anti-inflammatory activity, ArcA Immunol. Ther. Exp. 30,421 32,1982 Van Emelen, K., De Wit, T., Hoomaert, G.J., and Compemolle, R, Diastereoselective intramolecular... 

General Mechanism—Acid-Catalyzed Nucleophilic Addition 787... 

Problem 21.12 In acid-catalyzed aldol condensations acid is believed to perform two functions to catalyze conversion of carbonyl compound into the enol form, and to provide protonated carbonyl compound with which the enol can react. The reaction that then takes place can, depending upon one s point of view, be regarded either as acid-catalyzed nucleophilic addition to a carbonyl group, or as electrophilic addition to an alkene. On this basis, write all steps in the mechanism of acid-catalyzed aldol condensation of acetaldehyde. In the actual condensation step, identify the nucleophile and the electrophile. 

Steps 1-3 Acid-catalyzed nucleophilic addition of 1 mole of ethanol to the carbonyl group. The details of these... 

The results of the labeling experiment and the fact that esterifications are acid catalyzed are both consistent with the mechanism that follows. This mechanism is typical of acid-catalyzed nucleophilic addition-elimination reactions at acyl carbon atoms. 

A MECHANISM FOR THE REACTION ] Addition of a Strong Nucleophile to an Aldehyde or Ketone 733 [ A MECHANISM FOR THE REACTION ] Acid-Catalyzed Nucleophilic Addition to an Aldehyde or Ketone 733... 

Step 3 The species formed in the preceding step cyclizes to give the conjugate acid of P-D-glucopyranose. This cyclization is analogous to the acid-catalyzed nucleophilic additions to aldehydes and ketones in Chapter 17. 

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