Carboxylic acids, esters etc.

Objectives

•To continue to learn about the structures and some of the uses of acids, ethers and esters.

Carboxylic or organic acids

General formulae of organic acids is R-COOHFunctional group is a combination of the carbonyl group of aldehydes and ketones and the hydroxyl group of alcohols.

Organic acids facts

Made by the oxidation of alcohols – e.g. wine turns to vinegar as ethanol oxidises to ethanoic acid.

Classed as weak acids

Instead of a carbon chain (alkyl group) they may be attached to an aromatic group such as benzene.

Naturally occurring organic acids

Methanoic (formic) Ants and bee stings

Ethanoic (acetic) vinegar

Propanoic (propionic) milk products

Butanoic (butyric) Butter as it is going off (Rancid)

Alpha hydroxy acids which have a hydroxyl substituent on the carbon next to the carboxyl group are popular in skin treatments and naturally occur in fruit, milk and sugarcane, e.g.

Lactic acid: an alpha-hydroxy acid This is why Cleopatra is supposed to

have bathed in asses milk!

Esters

Comprised of an alcohol combined with an organic acid

Naming esters

Esters are very important in the creation of food flavourings etc.

This smells of pears

E.g an ester formed from propanol and ethanoic acid is called propyl ethanoate

The second is the name of the carboxylic acid changed to carboxylate

The first part is the alkyl name for the alcohol chain

The name is in two parts

Work these outWhich ester would you get from addingPentanol and

ethanoic acid (banana

flavour)

Pentanol and butanoic

acid (Apricots)

Octanol and ethanoic

acid (oranges

Ethers

Ethers general formula is R-O-R. so the oxygen joins two chains of carbons (alkyls)

You name them by writing the name of each alkyl or aryl group attached to the oxygen in alphabetical order followed by ether.

This is ethyl methyl ether – note incorrectly named on google!

Amines and Amides

Both contain nitrogens

Amines can be R-NH2 or R-NH-R or the N can be attached to three alkyl chains.

Several ways of naming them – we’ll use the common one

Name them by naming the alkyl chain then the amine e.g CH3-NH2 is methyl amine.

If two or three alkyl groups are attached to the amine then name them in alphabetical order

Uses of amines

Amines obviously form amino acids – the monomers of

proteins

Complex amines exist in our body

such as histamines that mediate immune and

allergic responses.

Amines in plants are often referred

to as alkaloids. Include caffeine morphine and

nicotine

Common simple amines are

intensely smelly and very toxic.

Amides

Are carboxylic acids where a nitrogen group has replaced the hydroxyl group

R-CONH2

They are produced by the neutralisation of carboxylic acids by ammonia or an amine

Propanoic acid + ammonia would make propanamide.

Propanoic acid + methyl amine would make methyl propanamide

Draw condensed structural formulae for

propanol

Pentanoic acid

1 bromo, 4 iodo pentane

Butyl methyl ether

Pentanal

Pentanone

Methly propanoate

Ethyl ,propyl amine

The amide created by the reaction of ethanoic acid with ethyl amine