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Carboxylic Acids

Carboxylic Acids

Background:


An acid as a "substance which donates protons (hydrogen ions) to other molecules". Carboxylic acids are acidic because the hydrogen contained in the -COOH group dissociates with the primary molecule to various degrees in order to release an H+ ion.

Physical Properties:


Carboxylic acids have have high boiling points.

Chemical Properties:


The carboxyl group is weakly acidic and all carboxylic acids neutralize OH-.

Typical of solutions of carboxilic acids in general ethanoic acid solutions can have pH value's in of 2 - 3, depending on their concentrations. Methanoic acid however is stronger than other simple acids, since its solutions have pH's about 0.5 pH units less than ethanoic acid for the same concentration.

Important Compounds and Derivatives:


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 write the name of the akyl group attached to the O, and follow it with the name of the parent carboxylic acid changing the suffix "ic acid" to "ate" in the process.

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 suffix "oic acid", with "amide".

Carboxylic acids react with some metals to produce a salt and hydrogen. The reactions are the same as with inorganic acids except they tend to be proceed more slowly.

Laboratory Preparation:


Carboxilic acids can be prepared by oxidizing a first degree alcohol, choosing the alcohol to have same carbon chain as the required acid.

Oxidation of the alcohol is carried out using an oxodizing agent such as potassium permaganate or potassium perchlorate. The first product of the oxidation will be the aldhyde derivative of the alcohol and the oxidation of the aldehyde using the same oxidizing agent will lead to the generation of the required carboxilic acid.

Naming Conventions:


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. For example:

HCOOH - methanoic acid (formic acid)
CH3COOH - ethanoic acid (acetic acid)
CH3CH2CH2COOH - butanoic acid (butyric acid)

Bibliography:


Wilipedia - article on carboxylic acid
Michigan State University - article on carboxylic acid
Perdue University - article on the carbonal group including carboxilic acid

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