6.2 Flashcards
(26 cards)
what does an ‘R’ group represent
alkyl chain of unspecified length
formula, bonding, shape and bond angle of ammonia
NH3 covalent bonding hydrogen bonding (inter molecular) 107.5 bond angle pyramidal shape ( 3 bonded pairs and one lone pair)
what does primary, secondary or tertiary refer to when talking about amines
the amount of R groups attached
primary has one r group, secondary 2, tertiary 3
are amines (and ammonia) bases or acids? why?
amines and ammonia are both weak bases (by both definitions) as amines have a lone pair of electrons for donations and are a proton acceptor) –> the lone pair on the nitrogen atom can be attacked by H+ ions (proton) forming a dative covalent bond
primary amine + acid –>
and what is special about the product
primary amine + acid –> ammonium salt
ammonium salts are completely nonmetal
what reagents are required for the preparation of aliphatic amines
haloalkane
excess ammonia and ethanol (or excess ethanoic ammonia)
what mechanism is used to make aliphatic amines
nucleophilic substitution of haloalkanes
what are the two steps in the preparation of aliphatic amines
1) react a haloalkane with ammonia to make a salt
(CH3CH2Br + NH3 –> [CH3CH2NH3]+Br-)
2) add excess ammonia to form an amine + ammonium
salt
( [CH3CH2NH3]+Br- + NH3 –> CH3CH2NH2 + NH4+Br-)
why is ammonia added in excess in the preparation of aliphatic amines
otherwise additional substitutions of the hydrogen atoms will occur making secondary and tertiary amines
why is the preparation of aliphatic amines done in a sealed container
because ammonia is very volatile and if the container wasn’t sealed it would be lost from the system.
what are the reagents and conditions in the preparation of aromatic amines
nitroarene (benzene with a NO2 group)
tin + conc. hydroclorc acid as a reducing agent
(sodium hydroxide- strong alkali) added after 30mins to neutralise any excess acid
conditions: 100C under reflux
what is an α-amino acid
an amino acid which the -COOH and the -NH2 functional groups are added to the same carbon
what two functional groups do α-amino acids have
carboxylic acid -COOH
amine group -NH2
general formula for α-amino acids
RCH(NH2)COOH
why are amino acids considered amphoteric
because the carboxylic acid functional group acts as a weak acid that will partially ionise in water
AND the amine group acts as a base due to the lone pair on the nitrogen atom
how can α-amino acids form zwitterions
becasue the two functional group groups exchange a proton and make an internal salt
COO- and NH3+ (charges cancel out)
what is the isoelectric point
is when there is no overall electrical charge due to each zwitterion having an internal balance
how will changing the pH have an effect on the charge of the ion
a lower pH (1) than the isoelectric point will make a postive ion (NH3+)
a higher pH (13) than the isoelectric point will make a negative ion (COO-)
what is an amide functional group
-C(=O)N(-H)
what do amino acids form when they react together
amino acids form a peptide in condensation reactions
what is the reverse of condensation reactions called
hydrolysis
when polypeptides/proteins are hydrolyses into separate amino acids
how can amides be made
- condensation of amino acids
- by mixing acyl chloride with ammonia
what are optical isomers
non-superimposable images of each other
same structure but are mirror images of each other
these molecules are entantiomers to each other (different entantiomers rotate plane polarized light in opposite directions)
what is a chiral molecule
a molecule with no plane of symmetry
