7) Notion about derivatives of carboxylic acids.

The important classes of organic compounds known as alcohols, phenols, ethers, amines and halides consist of alkyl and/or aryl groups bonded to hydroxyl, alkoxyl, amino and halo substituents respectively. If these same functional groups are attached to an acyl group (RCO–) their properties are substantially changed, and they are designated as carboxylic acid derivatives.

8)  СН-acidity of -carbon atom.

Acidity of Carboxylic Acids

• Carboxylic acids are much more acidic than alcohols.

• Two main reasons explain this acidity:

– Resonance stabilization of the conjugate base, RCOO^-

– Electrostatic stabilization of the negative charge by the adjacent polar carbonyl group.

Name	Formula	Structural formula	pKa
Methane	CH4		~ 56
n-Butyllithium	C4H9Li		~ 50
Ethane	C2H6		~ 50

9) Nucleophilic substitution reaction of sp2-hybridization carbon atom:

a) acylation reaction – formation of anhydrates.

b) reaction of complex ester, thioester, amides. Hydrolysis of these compounds.

1. The sp2 hybridization of the carbonyl compound means that attack of the

nucleophile on the carbonyl carbon may occur from either face.

• The resulting addition product is sp3-hybridized.

• We used the example of hydration (formation of gem-diols) to illustrate

• nucleophilic addition to carbonyl compounds; however, other nucleophiles can

• undergo the same reaction.

• There are other acid- and base-catalyzed examples.

The acid-catalyzed preparation of esters from carboxylic acids is known as Fischer esterification.

– Esters are carboxylic acid derivatives with the carboxylate -OH group replaced by an alkoxy group.

– Treating a carboxylic acid with an excess of an alcohol gives esters.

• This is an example of substitution at the carbonyl carbon.

• The reaction is driven forward by using a large excess of alcohol (usually as solvent), an application of Le Chatelier’s principle.

2. Hydrolysis under acidic conditions:

Taking ethanamide as a typical amide:

If ethanamide is heated with a dilute acid (such as dilute hydrochloric acid), ethanoic acid is formed together with ammonium ions. So, if you were using hydrochloric acid, the final solution would contain ammonium chloride and ethanoic acid.