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-COOH Functional 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 stingsEthanoic (acetic) vinegarPropanoic (propionic) milk productsButanoic (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 out Which ester would you get from adding Pentanol 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 propanolPentanoic acid1 bromo, 4 iodo pentaneButyl methyl etherPentanalPentanoneMethly propanoateEthyl,propyl amineThe amide created by the reaction of ethanoic acid with ethyl amine