Groups 11,12 and 13

Carboxylic Acids, Ethers and Esters

Today's Starter Quote“What lies behind us and what lies before us are tiny matters compared to what lies within us”

– Ralph Waldo Emerson

Oxidation of an alcohol will lead to an aldehyde or ketone. Further oxidation can lead to the formation of a carboxylic acid, where both an aldehyde and alcohol functional group are found. The overall appearance is -COOH where the group must be terminal.

Carboxylic acids are named by taking the typical alkane name and changing the suffix from ‘ane’ to ‘anoic acid’.

B. R. Travis, M. Sivakumar, G. O. Hollist, B. Borhan, Org. Lett., 2003, 5, 1031-1034.

Note: Ketones will not oxidize under standard conditions. So we will consider that ketone + (O) → NRAldehydes will test positive by the Tollen's test, whereas a ketone will not react in this manner.

(chem.wisc.edu)

Examples:1) HCOOH methanoic acid (formic acid) found in

ant bites(gcsescience.com/methanoic-acid)

2) CH3COOH ethanoic acid (acetic acid) found

in vinegar

3)CH3CH(OH)COOH 2-hydroxypropanoic acid (lactic acid)

Many common organic compounds contain more than one COOH group such as tartaric acid found in grapes, citric acid in fruits, ascorbic acid (Vitamin C) and acetylsalicylic acid found in aspirin.

(gcsescience.com/ethanoic-acid)

(bmrb.wisc.edu)

Carboxylic acids are quite polar since they have both an OH group and a carbonyl group. They are quite similar to alcohols, however have the characteristics of acids such as turning litmus paper red (an excellent test for this group only) and neutralizing base.

The structure of an ether is similar to water. Rather than a hydrogen on each side of the oxygen atom, there are carbon chains. The two groups may be identical (ROR)or different( R –O-R’). There is no possibility to form hydrogen bonds since there are no OH groups, however the boiling point is intermediate between the alkane and alcohol as they are somewhat polar.

Ethers are good solvents since they mix well with polar and non-polar liquids. They are unreactive due to the trapped O, which makes it an even better solvent.

Ethers

Ethers are named by adding oxy to the smaller group and joining it to the alkane name of the longer chain. Examples: CH3CH2OCH2CH2CH3 ethoxypropane

CH3OCH3 methoxymethane

CH3OCH2CH3 methoxyethane

Ethers are made by condensation reactions. This is another word for a dehydration reaction. By adding two alcohols in the presence of strong acid, it is possible to make an ether.

H2SO4

Example: CH3OH + CH3CH2OH --> CH3OCH2CH3 + HOH Methanol ethanol methoxyethane

water

Esters:Formation of an ester occurs when a carboxylic acid is

reacted with an alcohol in the presence of a strong acid and heat. The result is an ester with the group C(=O)O-R where R is another alkyl group. Water is also made. Esters are easily characterised by their distinct odour, often used in artificial flavouring. The reaction may occur as :

Acid and heatButanoic acid + methanol --> methyl butanoate + water

(an apple odour)NOTE: when naming esters, the first part of the name is derived from the part that came from the alcohol. It also will not have a carbonyl group. The second part of the name comes from the carboxylic acid that retains the carbonyl group.

Examples: ethyl benzoate C6H5COOCH2CH3

octyl ethanoate CH3COO(CH2)7CH3 ethyl butanoate CH3CH2CH2COOCH2CH3

ethyl methanoate HCOOCH2CH3