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Naming Carboxylic Acids
The parent chain must include the carboxyl carbon, which is given position number 1.
The name of the alkane attached is changed by replacing the -e with -oic acid.
Because carboxylic acids have both a lone oxygen and an OH group, they are strongly hydrogen-bonded to each other, therefore having high boiling points.
ethanoic acid (acetic acid)
The carboxyl group is weakly acidic and all carboxylic acids neutralize OH-.
RCOOH + NaOH ==> RCOONa + H2O
Esters of Carboxylic Acids
Carboxylic acids are used to synthesize two important derivatives, esters and amides.
In esters, the OH of the carboxyl group is replaced by OR.
To name esters, first have the name of the akyl group attached to the O, followed by the name of the parent carboxylic acid after its name is altered by changing -ic acid to -ate.
Esters are responsible for or mimic many pleasant fragrances in nature.
In an mixture with carboxylic alcohol, an equilibrium reaction forms ester and water in the presence of heat and a strong acid catalyst.
RCOOH + HOR' <==> RCOOR' + H2O
CH3CH2CH2COOH + HOCH2CH3 <==> CH3CH2CH2COOCH2CH3 + H2O
butanoic acid + ethanol <==> ethyl butanoate + water
Hydrolysis and Saponification of Esters
An ester is hydrolyzed to its parent acid and alcohol when it is heated together with a stoichiometric excess of water (with acid catalyst)--this is the reverse of the reaction above.
Saponification, is the reaction of an ester with a strong base, like sodium hydroxide.
CH3COOCH2CH3 + NaOH ==> CH3COO- + Na+ + HOCH2CH3
ethyl ethanoate + sodium hydroxide ==> ethanoate ion + sodium ion + ethanol
sodium ethanoate salt
The mixtures of salt of long-chain carboxylic acids are the ingredients of ordinary soap.
Amides of Carboxylic Acids
In amides, the OH of the carboxyl group is replaced by nitrogen holding any combination of H atoms or hydrocarbon groups.
The names of simple amides are devised by writing the name of the parent carboxylic acid and replacing the ending, -oic acid, with -amide
The preparation of simple amides are similar to those of esters, but they are in an excess of ammonia.
RCOOH + NH3 ==> RCONH2 + H2O
carboxylic acid + ammonia ==> simple amide + water
When amides are in water, they are changed back to the carboxylic acid and ammonia.
Unlike amines, the amides are nonbasic even though they have the NH2 group in simple amides.
This is because of the O atom in the carbonyl group, which is very electronegative.
This tightens the electrons on N so that it is unable to accept a proton.