Amines and their preparations

Question 1

nitrogen has … bonding pairs of electrons

Answer 1

3 bonding pairs

Question 2

in amines, the 3 bonding pairs of electrons are distributed in a …………… shape

Answer 2

trigonal pyramidal shape

Question 3

in amines, as in ammonia, the nitrogen atom has ……………… which influence its reactions

Answer 3

a pair of lone electrons

Question 4

the 3 types of amine that exists are:

their general formulae are:

Answer 4

• primary, secondary and tertiary, depending on how many alkyl groups are bonded to the nitrogen atom
• primary: RNH2
• secondary: RNHR
• tertiary: RNR2

Question 5

methylamine is a………. at room temperature

Answer 5

gas

Question 6

ethylamine has a boiling temperature of

Answer 6

17 degrees C

Question 7

propylamine and butylamine are both……………………at room temperature

Answer 7

volatile liquids

Question 8

the method for preparing an amine starting from a halogenoalkane is

Answer 8

• heating a halogenoalkane with ammonia
• this is done under pressure and in a sealed container because ammonia is a gas
• alternatively this can be done by mixing the halogenoalkane with concentrated NH3

Question 9

the equation for the preparation of ethylamine is

Answer 9

CH3CH2Cl + NH3 → CH3CH2NH2 + HCl

Question 10

the reaction between ammonia and a halogenoalkane involves ……………….. attack by the …………….. on the ………………..

Answer 10

involves nucleophilic attack from the lone pair of electrons of NH3 on the electron deficient carbon atom of the halogenoalkane

Question 11

because the amine formed in the reaction between a halogenoalkane and NH3 also has a lone of electrons, it then……

Answer 11

the amine then competes with the NH3 remaining int eh reaction mixture to act as another nucleopphile and react with unreacted halogenoalkane to form a secondary amine

Question 12

the equation for the reaction between methylamine and chloromethane is

Answer 12

CH3Cl + CH3NH2 → (CH3)2NH + HCl

dimethylamine is formed, a secondary amine

Question 13

to prevent unwanted side reaction involiving the primary amine and the halogenoalkane, we use

Answer 13

excess NH3

Question 14

the equation showing the reaction between chloromethane and excess NH3 is

Answer 14

CH3Cl + 2NH3 → CH3NH2 + NH4Cl

Question 15

the method for preparing a primary amine from a nitrile is :

Answer 15

• reducing a nitrile, for example CH3CN, to an amine using sodium tetrahydridoaluminate (NaAlH4)
• the reactants must be mixed with ether to ensure dry conditions so no water affects the reaction

Question 16

the equation showing the reduction of ethanitrile to ethylamine is

Answer 16

CH3CN + 4[H] → CH3CH2NH2

[H] represents the atoms from the NaAlH4 reagent

Question 17

phenylamine is made from the reduction of

Answer 17

nitrobenzene

Question 18

the method for the reduction of nitrobenzene to make phenylamine is :

Answer 18

• use the reducing agent tin mixed with ocncentrated hydrochloric acid
• heat the reaction mixture under reflux
• the reduction is achieved from the reduction of tin to tin(II) ions and tin(IV) ions and partly through the hydrogen produced in the reaction between tin and the acid

Question 19

the equation that represents the reduction of nitrobenzene to phenylamine is

Answer 19

C6H5NO2 + 6[H] → C6H5NH2 +2H2O

Question 20

because, as all amines, phenylamine is ………………. , it will react with the acid in the mixture to form……………
this ion can easily be converted back to phenylamine when a………………… is added

Answer 20

• phenylamine is basic
• will form phenylammonium ion (C6H5NH3+)
• can be converted when a base such as sodium hydroxide is added

Question 21

nowadays, phenylamine is used in the manufacture of: (2 itmes)

Answer 21

• synthetic indigo

- used to make polymers and pharmaceuticals