Chapter 27 - Amines, Amino Acids and Polymers Flashcards
define what an amine is
“Amines are organic compounds derived from ammonia in which one or more hydrogen atoms in ammonia have been replaced by a carbon chain or ring”
what is the difference between primary/secondary/tertiary amines
primary = 1 alkyl/acyl group is substituted secondary = 2 alkyl/acyl groups are substituted tertiary = 3 alkyl/acyl groups are substituted
how to name amines where a single hydrogen has been replaced by a straight/branched carbon chain
if at the end of a chain simply add amine e.g. butylamine
if at a point other than the end on the chain add a number and amino e.g.
2 aminobutane
how to name amines where two or more hydrogens have been replaced by the same type of carbon chain
add di… or tri…
e.g. dimethylamine
how to name amines where 2 or more different groups are substituted for hydrogens
do N - smaller group, bigger group amine
e.g.
N-methyl propylamine
what is the main way that amines can react and why
- they can react by acting as a base, they contain a lone pair on the nitrogen that is able to accept a proton to form a daitive covalent bond, producing an ion
what occurs when an amine reacts with an acid
- they act as a base to neutralise the acid
- the NH2 goes to NH3+ and bonds with the anion of the acid
how can we prepare aliphatic amines, state the conditions
1) react a haloalkane with ammonia to form an alkyl ammonium salt (like in the salt-acid reactions)
2) react the salt formed with excess aqueous alkali e.g. NaOH to form a primary amine and other products (often salt and water)
conditions:
1) use ethanol as a solvent
2) use excess ammonia
explain why we use these conditions in the production of aliphatic amines
1) we use ethanol as a solvent to prevent the hydrolysis of haloalkanes to alcohols
2) we use an excess of ammonia to prevent further substitutions of the primary amine
explain what occurs in the preparation of primary amines/ what sort of mechanism it is
- ammonia can act as a nucleophile in a substitution reaction as it can donate its lone pair
- so it is nucleophilic substitution
explain why this reaction is not suitable for producing pure primary amines
once the first substitution has taken place to form a primary amine, the N atom still has a lone pair, this can further react with the haloalkanes to form a secondary amine, this can occur again to form a tertiary amine
explain the method for producing aromatic amines
- reduce nitrobenzene using concentrated hydrochloric acid and a tin catalyst
- the nitrobenzene and conc HCl act as a reducing agent [H]
- then react the salt formed with excess alkali to form an amine
C6H5NO2 + 6[H] —–> C6H5NH2 + 2H2O
define an amino acid
“Amino acids are organic compounds containing both the amine, NH2, group and the carboxylic acid, COOH, group”
explain what an Alpha amino acid is
where the amine group is attached to the 2 carbon, the alpha carbon, i.e. the carbon adjacent to the carboxylic acid group
they have the general formula
RCH(NH2)COOH
what do amino acids form in acidic solutions
- positive ions
- NH2 acts as a base and forms NH3+
- this can form salts as amines usually do
what do amino acids form in alkaline solution
- negative ions
- COOH acts as an acid and forms COO-
- this can also form a salt (and sometimes water)
how do amino acids react with alcohols and how is this different to carboxylic acids
- they form esters just like carboxylic acids
- but because this reaction is done in the presence of a conc. H2SO4 catalyst, they also form NH3+ on the amino group
what are the 4 main things to remember about Zwitterions
- at intermediate pHs (isoelectric points), Zwitterions form
- the exact pH depends on the amino acid
- these have both positive and negative charges on different parts of the molecule as the NH2 group acts as a base and the COOH group acts as an acid
- they have ionic bonding due to the opposite charges
