chapter 27 Flashcards
what are amines?
organnic compounds derived from ammonia NH3, in which 1 or more hydrogen atoms in ammonia have been replaced by a carbon chain (aliphatic amine) or ring (aromatic)
classifying amines
primary, secondary or tertiary by number of alkyl or aryl groups
primary, R–NH2
secondary, R, R’–NH
tertiary, R, R’, R”–N
amines in nature
serotonin, neurotransmitter, control of appetite, sleep, memory & learning, temperature regulation, muscle contraction & depression
pseudoephedrine, active ingredient in decongestion medicines, works by shrinking nasal membranes & inhibiting secretions
naming amines
primary- adding suffix -amine to name of alkyl chain, if not on carbon 1- named using prefix -amino, and a number is added to indicate position on chain
eg ethylamine, 2-aminobutane
tertiary/secondary- same alkyl group, prefixes di or tri used- indicate number of alkyl groups attached to nitrogen eg dimethylamine
-when 2 or more diff groups attached to nitrogen, named N-substituted derivative of the larger group
eg CH3NHCH2CH3 is N-methylpropylamine
amines as bases
lone pair of electrons on nitrogen can accept a proton
when accepted, forms a dative covalent bond
salt formation
neutralise acids to make salts
eg propylamine w/ HCl- propylammonium chloride
CH3CH2CH2NH2 + HCl –> CH3CH2CH2NH3+ Cl-
ethylamine w/ sulphuric acid- ethylammonium sulfate
2CH3CH2NH2 + H2SO4 –> (CH3CH2NH3+)2 SO42-
formation of primary amines, reaction & conditions
ammonia has a lone pair which allows it to act as nucleophile in substitution w/ a haloalkane forming an ammonium salt, aq alkali is added to generate the amine from the salt
salt formation:
CH3CH2CH2Cl + NH3 –> CH3CH2CH2 NH3+ Cl-
1-chloropropane propylammonium chloride
amine formation:
CH3CH2CH2NH3+ Cl- + NaOH –> CH3CH2CH2NH2 + NaCl + H2O (propylamine)
conditions
-ethanol=solvent, prevents any substitution of haloalkane by water- alcohol
-excess ammonia used, reduces further substitution of amine group
formation of secondary & tertiary amines
primary product still has lone pair can react further w/ haloalkane- secondary, produces a salt
CH3CH2CH2Cl + CH3CH2CH2NH2 –> (CH3CH2CH2)2NH2+Cl-
propylamine–> dipropylammonium chloride osalt)
secondary amine is obtained by reacting w/ NaOH
(CH3CH2CH2)2NH3+Cl- +NaOH –> (CH3CH2CH2)2NH (dipropylamine) +NaCl + H20
tertiary can be formed by further reaction eg tripropylamine (CH3CH2CH2)3N
preparation of aromatic amines
phenylamine, C6H5NH2 made by reduction of nitrobenzene C6H5NO2. heated under reflux w/ tin ND HCl to form ammonium salt- phenyl ammonium chloride which is reacted w/ excess NaOH to produce phenyl amine
Tin & HCl act as reducing agents
C6H5NO2 + 6[H] —1 Sn/conc HCl—–2 excess NaOH—-> C6H5NH2 +2H20
amino acids
organic compound containing both amine and carboxylic acid functional groups
RCH(NH2)COOH
reactions of the amine group
basic and reacts w/ acids to make salts
eg alanine w/ HCl
NH2CH(CH3)COOH + HCl–> NH3+CH(CH3)COOH + Cl-
reaction of carboxylic group w/ aq alkali
eg sodium or potassium hydroxide, form salt and water eg glycine (aminoethanoic acid) w/ NaOH
NH2CH2COOH + NaOH—> NH2CH2COO-Na+ + H2O
carboxylic group- esterification with alcohols
easily esterified by heating w/ an alcohol in presence of conc sulfuric acid
eg sterine w/ excess ethanol & some sulfuric acid
NH2C(CH2OH)HCOOH + C2H5OH + H+ —> NH3+C(CH2OH)HCOOC2H5 + H2O
amides
products of reactions of acyl chlorides w/ ammonia & amines
primary- one carbon atom bonded to N
secondary- 2 carbon atoms bonded to N
tertiary- 3 carbon atoms bonded to N
Optical isomerism
found in molecules that contain a chiral centre= a carbon atom attached to four different atoms/groups of atoms
-presence of chiral carbon atom leads to existence to 2 non-superimposable mirror images- optical isomers/ enantiomers
for each chiral carbon- one pair of isomers
