OCR A 6.2.1 and 6.2.2 Amines, Amino Acids, Amides and Chirality

amine

-derived from ammonia molecules

-all contain a N atom

-H are replaced w/ organic group

aliphatic amines

-primary; methylamine

-secondary; dimethylamine

-tertiary; trimethylamine

-quaternary ion; tetramethylamine ion

aromatic amine

-primary amine; phenyl amine

amine properties

-act as base

amine as a base

-have lone pair of e that allows them to accept a proton

-when proton bonds to amine via a dative covalent bond; both e in bond come from lone pair in N

what does the strength of amine as a base depend on

-availability of the lone pair of e on N

-higher e density; more readily available the e are; more basic

what does electron density of N depend on

-type of group attached

-the more e on grp the higher e density

-unless phenol as lone pair goes to benzene ring

amine + acid reaction

-neutralise acid to make salt

how to prepare primary amines

-reduction of halogenoalkanes with ammonia

-reduction of nitriles

reduction of halogenoalkanes with ammonia

-nucleophilic substitution

-lone pair on N acts as nucleophile and replaces halogen

-ethanol used as solvent; prevents sub of haloalkane to make alcohol

-excess ammonia used; further sub of amine group to secondary/tertiary amine

reduction of nitrile

-C-N func grp can be reduced to NH₂

-reacting with H₂ gas in presence of Ni catalyst

preparation of secondary amine

-react excess haloalkane w/ primary amine

-in ethanol

react haloalkane w/ primary amine

-nucleophilic substitution

-N in amine acts as nucleophile and replaces halogen

-condition:

preparing aromatic amine

-nitrobenzene can be reduced to phenylamine

-reduction; reacted with Sn and conc HCl which acts as reducing agent

-heated under reflux in boiling water bath

-phenylammonium salt forms

-addition of excess NaOH sol to produce aromatic amine

amino acids

-organic compounds that contain 2 func grps

-amino grp;-NH₂

-carboxyl grp; -COOH

general formula a-amino acid

-RCH(NH2)COOH

amino acid property

-has basic amino grp and acidic carboxyl group

-can act as acid and base

-undergo most reactions of amines and carboxylic acids:

-amines with acids

-carboxylic acids with bases

reaction of amine group

-reacts with acids to make ammonium salt

reaction of carboxyl group with aqueous alkali

-amino acid reacts w/ aqueous alkali such as Na/KOH to form salt and water

esterification of amino acid with alcohol

-amino acid can be esterified by heating with alcohol

-in presence on conc H₂SO₄

-carboxyl grp is esterified

-amine grp protonated due to acidic condition

amides

-formed from condensation reaction of acyl chloride w/ ammonia and amides

name

o

optical isomer

-form of stereoisomerism

-same structural formula but dif arrangement of atoms in space

-mirror images of each other

-have chiral carbon atom

chiral centre

has 4 dif groups attached to C atom

how to detect optically active compounds

-they rotate plane polarised light

-D enantiomer rotates light clockwise

-L enantiomer rotates light anti-clockwise

how to get plain polarised light

-standard oscillates in all directions

-pass light thru a polaroid filter

-light will only oscillate in 1 direction