amines

a nitrogen compound in which 1 or more of the H atoms in NH3 has been replaced by an alkyl group they are very reactive compounds which are useful in the production of new molecules they have a lone pair

the N is directly joined to the benzene ring

they contain quaternary ammonium ions and are related to amines, but are not amines and do not possess a lone pair of electrons on the N

primary- 1 alkyl group attached to the N atom secondary- 2 alkyl groups attached to the N atom tertiary- 3 alkyl groups attached to N atom

named using suffix -amine (higher priority than alkyl) if more than one alkyl group is present, they are listed alphabetically if other functional groups are present, the presence of amine groups is denoted using the ‘amino’ prefix

trigonal pyramidal shape with a bond angle of 107 degrees C the lone pair exerts a stronger repulsive force so reduced the bond angles by 2.5 degrees

very similar shape with bond angles of 107 degrees between the R groups on the N atom

primary amines can form hydrogen bonds with each other BUT alcohols will have a higher boiling point because O is more electronegative than N so hydrogen bonding will be stronger

short chain amines are gases at room temperature, longer chains are volatile liquids those with low boiling points smell like ammonia, whereas those that are liquid at room temp have fishy aromas

also form hydrogen bonds, but as the N atom is in the middle of the H-C chain, the strength of the dipole is slightly less, so the strength of dipole-dipole attractions decreases

there is no H attached directly to the N atom, so H bonding between molecules is impossible only permanent dipole- permanent dipole

longer chain amines are only sparingly soluble, as the larger alkyl groups interfere with the H bonds shorter chain amines (<C4) are very soluble in water and alcohols, as the lone pair on the N atom allows them to form H bonds phenyl amine is not very soluble, partial delocalisation of lone pair and disruption of water H bonds

ammonia has a lone pair of electrons that allow it to act like a nucleophile

initially forms primary amines but the amines produced also have a lone pair on the N atom, so they cab react with halogenoalkanes which means that the H’s on the N can be successively replaced by the R group from the haloalkanes, right through to quaternary ammonium salts this greatly complicates the reaction, because any amine produced in such a reaction can react with more haloalkane and undergo further substitution

if a large excess of ammonia is used, a primary amine is the main product if a large excess of the haloalkane is used, a quaternary ammonium salt is the main product

a mixture of amines and ammonium salts is produced which would have to be seperated

cationic surfactants surfactants are molecules that reduce surface tension and allow mixing of two substances that might not normally mix so these salts are commonly used in fabric softeners, hair conditioners, and sewage flocculants because the positive nitrogen is attracted to the negative surfaces such as glass, plastic and hair

• nitration of benzene- conc sulfuric acid and nitric acid • reduction of nitrobenzene- Sn catalyst and conc HCl as this reaction is carried out, a salt will be formed, which can be reacted wit NaOH to give the phenylamine

reduction of nitrile compounds which only forms one amine rather than a mixture, it has two steps

• formation of nitrile from a halogenoalkane, by reacting with potassium cyanide, warm in ethanol (they can also be formed by reacting a cyanide ion with a ketone or aldehyde to form a hydroxynitrile) • reduction of nitrile to form an amine with EITHER H2 with a Ni catalyst (called catalytic hydrogenation) OR LiAlH4 in dry ether then dilute acid

although there is a higher chance of primary amines, because it is a two step process, there are more possible steps where product might be lost and so yield might be lower

• nucleophilic substitution of haloalkane with ammonia • nitration of benzene followed by reduction of Sn/HCl • nucleophilic substitution of haloalkane with potassium cyanide to make a nitrile, followed by reduction with LiAlH4 in dry ether

amines react with acyl chlorides and acid anhydrides to replace a H on the N with the acyl group this produces an amide and a molecule of HCl or a carboxylic acid a second molecule of the amine reacts with the HCl/ carboxylic acid to form a salt