organic nitrogen compounds

Question 1

bascitiy of amines

Answer 1

ammonia and the amines act as bases = accept hydrogen because of the lone pair on the nitrogen.
donates lone pair to H+ ion to form dative bond

Question 2

nh3 + hcl

Answer 2

nh3 + hcl –> nh4+cl-

CH3NH2 + HCl –> CH3NH3+Cl-

Question 3

strengths in bascity of amines and ammonia

Answer 3

ethylamine > ammonia > phenylamine
ethyl group is electron donating, positive inductive effect which makes the N atom more readily avaible to bond with H+ ion
ammonia doens’t have any alkyl groups
phenylamine because one of the p orbitals of nitrogen overlap in the pi bonding system in the benzene ring which makes the lone pair delocalised and less avaible to form dative bond than ammonia

Question 4

ways to form amine

Answer 4

1- bromoethane
2- form a nitrile to make amine
3- reduction

Question 5

bromoethane to form primary amine

Answer 5

CH3CH2Br + NH3 –> CH3CH2NH2 + HBr
use excess hot ethanolic ammonia under pressure to prevent forming secondary and tertirary amines
excess ammonia (NH3 + HBr –> NH4Br) to prevent the HBr reacting with ethylamine = also prevents nucleophile, CH3CH2NH2 to attack

Question 6

bromoethane to form secondary amine

Answer 6

secondary amine:
halogenalkane and primary amin and react again in ethanol, heat in sealed tube and under pressure.
CH3CH2NH2 + CH3CH2Br –> (CH3CH2)2NH + HBr

Question 7

nitiles and halogenalkane

Answer 7

CH3Br + CN- –> CH3CN + Br-
potassium cyanide, KCN in ethanol, heat, reflux
bromo methane not ethane because carbon is added from CN-
then CH3CN + 4[H] – > CH3CH2NH2 (ethylamine)
nitrile vapour and hydrogen gas are passed over nickel catalyst or LiAlH4 in dry ether

Question 8

reduction from amides to amines

Answer 8

CH3CONH2 (ethanamide) + 4[H] –> CH3CH2NH2 + H2O

LiAlH4 in dry ether

Question 9

make phenylamine

Answer 9

reducing nitrobenzne
heat, reflux with tin (Sn) and conc HCl
C6H5N+H3 –> C6H2NH2 (phenylamine) with NaOH
B(benzene ring)-NO2 + 6[H] –> B-NH2 + 2H2O
separated with steam distillation

Question 10

phenylamine with bromine

Answer 10

NH2 group on phenylamine has lone pair of electrons which is delocalised in pi bonding system
extra electron density in the benzene ring is more readily attacked by electrohiles
2,4,6 positions attacked with NH2 (electron donating group)

B-NH2 + 3Br –> tribromophenylamine + 3HBr

Question 11

dyes with phenylamine

Answer 11

phenylamine and nitrous acid (HNO2) = diazotisation
B-NH2 + HNO2 + H+ –> B-N+= =N (triple bond) + 2H2O
kept below 10degress celcius = otherwise diazonium ion will decompose and form N2 gas

B-N+= =N (diazonium ion) acts as an electrophil and attacks the phenol so it becomes B-N=N-B-OH + H+

the pi bonding system is between two benzene rings which forms 4-hydroxyphenyloazobenzene(orange) = very stable
other aryl compounds other than phenol like B-N(CH3)2 can make yellow

Question 12

amino acids

Answer 12

amphoteric, basic amino group(-NH2) and acidic CA (-COOH) also neutral when R is alkly group
zwitterion = carries two charges, both acidic and basic properites.
if pH lowers, acid added, H+ accpeted, reforming COOH group, positively charged (COO- to COOH) and NH3+ remains
if pH increases, base added, NH3+ will donate an H+ ion so negatively charged (NH3+ to NH2) and COO-
adjusting pH by small amounts we can find where there neither poritive nor negtive ions dominate and no charge overall = isoelectric point

Question 13

isoelectric point

Answer 13

the pH value at which there is no overall charge on a particular amino acid in its aqueous solution
found when measuring the pH value of amino acid solution when its not attracted to positive or negative elecltrode (electrophoresis)

Question 14

making amides

Answer 14

acyl chlorides with ammonia
CH3COCl + NH3 –> CH3CONH2 + HCl
acyl chlorides with primary amine
CH3COCl + CH3CH2NH2 –> CH3CONHCH2CH2+ HCl
occur at room temp, white fumes of hcl.
excess amine will react with the HCl to form a salt, CH3CH2NH3+Cl-

Question 15

hyrdolysis of amides with acid

Answer 15

-CONH- can be hydrolysed with acid, eg HCl
NH leaves and replaced with OH to form COOH and goes to form NH2 or in excess H+, NH3
CA and primary amine
amine will further react with excess acid to form ammonium salt NH3+Cl- with HCl

Question 16

hyrdolysis of amides with alkali

Answer 16

NaOH(aq) form products of a sodium salt of the CA and the primary amine

Question 17

reflux amide (RCONH2) with acid

Answer 17

CA and ammonia

ammonia and react with excess acid to form ammonium salt

Question 18

reflux amide (RCONH2) with alkali

Answer 18

salt of CA and ammonia

Question 19

electrophoresis

Answer 19

It works because ions move at different rates towards the oppositely charged electrode
depending on the size / mass of ions
and charge on the ions;
larger ions will move more slowly;
more highly charged ions will
move more quickly.