FROM CARBOXYLIC ACID AND ALCOHOLS

Carboxylic acids react with alcohols to form esters in the presence of an acid catalyst. In the esterification reaction —OH is removed from the acid and —H removed from the alcohol to form water. Such reactions are equilibrium reactions and are very slow. 

The yield of an esterification reaction is low. There are large amounts of acid and alcohol left in the reaction mixture. The use of an excess of either the carboxylic acid or the alcohol increases the yield. The yield of an esterification reaction can also be increased by removing water from the reaction mixture as is formed. 

What is the molar mass and possible formula of the ester that is formed from a monocarboxylic acid with molar mass 60 g/mol and a monoalcohol with molar mass 46 g/mol (C 12 g/mol, H 1 g/mol, 0 16 g/mol) 

If we check the molar masses of the acid and alcohol, the correct formulae of the acid and alcohol are CH3COOH and C2H5OH respectively. So the structural formula of ester is O 

Acid anhydrides and acid chlorides react with alcohols to produce esters. 

---

Table 3-1. Monoesters prepared from carboxylic acids and alcohols or phenols using AyV -carbonyldiimid-azole (CDI), N-acylimidazole (RCOIm), or AyV -sulfinyldiimidazole (ImSOIm).

Table 3-2. Diesters prepared from carboxylic acids and alcohols using A -carbonyldiimidazole (CDI).

Preparation of carboxylic esters from carboxylic acids and alcohols H+ R-C-OH + R OH R-C-OR +H20 II II 0 0... 

Very important compounds are the carboxylic acids and their derivatives, which can be formally obtained by exchanging the OH group for another group. In fact, derivatives of this type are formed by nucleophilic substitutions of activated intermediate compounds and the release of water (see p. 14). Carboxylic acid esters (R-O-CO-R ) arise from carboxylic acids and alcohols. This group includes the fats, for example (see p.48). Similarly, a carboxylic acid and a thiol yield a thioester (R-S-CO-R ). Thioesters play an extremely important role in carboxylic acid metabolism. The best-known compound of this type is acetyl-coenzyme A (see p. 12). 

Esters can be prepared from carboxylic acids and alcohols provided an acidic catalyst is present,... 

Esters, RC02R, are formed from carboxylic acids and alcohols in the presence of acid catalysts. The key step in esterification is the nucleophilic attack of a neutral alcohol molecule, R OH, at the carbonyl carbon of the conjugate acid of the carboxylic acid, RC(OH)2 , 6 ... 

Since esters are derived from carboxylic acids and alcohols, they are named by first identifying the alcohol-related part and then the acid-related part, using the -ate ending. Ethyl acetate, for example, is the ester derived from ethanol and acetic acid. 

Braga, D., Grepioni, F., Sabatino, P., Desiraju, G. R., Hydrogen-bonding in organometallic crystals. 1. from carboxylic-acids and alcohols to carbonyl-complexes. Organometallics 1994, 13, 3532-3543. 

The generation of oxygen-centered radicals from carboxylic acids and alcohols with the tandem reagent, PhI(OAc)2-l2, is an established practice... 

Examples of alkylation, dealkylation, homologation, isomerization, and transposition are found in Sections 1, 17, 33, and so on, lying close to a diagonal of the index. These sections correspond to such topics as the preparation of acetylenes from acetylenes carboxylic acids from carboxylic acids and alcohols, thiols, and phenols from alcohols, thiols, and phenols. Alkylations that involve conjugate additions across a double bond are found in Section 74 (alkyls, methylenes, and aryls from olefins). 

You can t make esters from carboxylic acids and alcohols under basic conditions because the base deprotonates the carboxylic acid (see p. 288). However, you can reverse that reaction and hydrolyse an ester to a carboxylic acid (more accurately, a carboxylate salt) and an alcohol. 

You remember, of course, that esters can be made from carboxylic acids and alcohols under acid catalysis, so you might expect them to use this type of method. On a small scale, it s usually better to convert the acid to an acyl chloride before coupling with an alcohol, using pyridine (or DMAP + Et3N) as a base this type of reaction might have been a reasonable choice too. 

Under almost anhydrous conditions in organic medium, lipases can be used in the reverse mode for direct ester synthesis from carboxylic acids and alcohols, as well as transesterifications (acyl transfer reactions) which can be divided into alcoholysis (ester and alcohol), acidolysis (ester and acid), and interesterification (ester-ester interchange). The direct esterification and alcoholysis in particular have been most frequently used in asymmetric transformations involving lipases. The parameters that influence enzymatic catalysis in organic solvents have been intensively studied and discussed. ... 

Esters from carboxylic acids and alcohols under acid catalysis the Aac2 and Ancl mechanism... 

Esters from Carboxylic Acids and Alcohols via Hydroxy Group Activation (HGA)... 

Gancet, C Preparation of Esters of Carboxylic Acids Directly From Carboxylic Acids and Alcohols Using a Catalyst System Comprising a Sulfonic Acid and a Polymer-Bound Tertiary Amine. European Patent 1,167,337, Jan 2, 2002. 

Diphenylammonium triflate, toluene, 80°C, 33-97% yield. This catalyst can also be used to prepare esters from carboxylic acids and alcohols, 78-96%... 

The Yamaguchi esterification utilises 2,4,6-trichlorobenzoyl chloride, also known as the Yamaguchi reagent, to form esters from carboxylic acids and alcohols. 

N 0 Me 0 From hydroxymethyl polystyrene by treatment with COClj, HjNNHCOjMe and NBS or Cl,.2i Mitsunobu reactions esters from carboxylic acids and alcohols lactones from hydroxy acids A/-aUcylation of phthalimides, a-alkylation of cyanoacetate carbodiimides from thioureas. ... 

Sn2 nucleophilic substitutions take place in scC02. The presence of silica-supported onium salts 42 as a phase-transfer catalyst enhances the reaction (Scheme 72). Esters formation from carboxylic acids and alcohols via dehydration also proceeds in scC02. The conversion increases as the CO2 pressure increases. A single homogeneous phase is obtained around the critical point, at which the conversion is maximized. 

Explain why direct ester formation from carboxylic acids and alcohols works in acid solution but not in basic solution. By contrast, ester formation from alcohols and acid anhydrides or chlorides is commonly carried out in basic solution in the presence of bases such as pyridine. Why does this work. ... 

The structure and nomenclature of sulfonate esters (see 113, 114, or 115) are described in Chapter 20 (Section 20.11.2). It is also true that sulfonate esters are good leaving groups in the substitution reactions described in this chapter (see Section 11.2.4). Sulfonate esters are prepared by the reaction of sulfonic acids with alcohols—much the way that carboxylic acid esters are prepared from carboxylic acids and alcohols (described in Chapter 20, Section 20.11.2). More commonly, sulfonate esters are prepared by the reaction of a sulfonyl chloride (see 112) with an alcohol. This reaction is also described in Chapter 20. This section presents only a simple preview of that chemistry, with the goal of showing that it is easy to convert alcohols into sulfonate esters, which are then useful as leaving groups in substitution reactions. The formal mechanism of these reactions will be discussed in Chapter 20. 

Just as esters are formed from carboxylic acids and alcohols in the presence of dicyclohexylcarbodiimide (DCC see Section 20.5.4), so amides are formed from amines (or ammonia) and carboxylic acids. The mechanism is identical to that presented for 77 80 using DCC, but the nucleophile is an amine rather than... 

Carboxylic acids are used as intermediates in the preparation of esters, amides, acid anhydrides, and acid chlorides. Esters are formed from carboxylic acids and alcohols when the mixture is heated in the presence of a mineral acid... 

Rationalize why esters are most effectively formed with acid catalysis from carboxylic acids and alcohols, but more effectively hydrolyzed under basic conditions. 

---