Halogenalkanes

Question 1

Reactivity of halogenalkanes

Answer 1

C-X bond is polar, difference in electronegativity. C is always slightly electron deficient. Polarity of C-X bond decreases down group. C atoms attract nucleophiles (slightly negative w/ a lone pair of electrons).

Question 2

Hydrolysis

Answer 2

Water is polar, delta - charge in water attracted to delta + charge in C. Products are colourless liquids, no colour change seen.
RX+H2O -> ROH + HX
OR
RX + H2O -> ROH + H^+ + X^-

Question 3

Making alcohols method 1

Answer 3

RX —KOH(aq)/heat under reflux-> ROH
Attacking nucleophile: OH- ion. Example w/ 1-chloropropane into propan-1-ol:
CH3CH2CH2Cl + KOH -> CH3CH2CH2OH + KCl

Question 4

Making nitriles

Answer 4

RX —KCN/heat under reflux-> RCN
RX heated with potassium cyanide dissolved in ethanol. Nucleouphile: CN- ion. Example w/ bromoethane into propanenitrile:
CH3CH2Br + KCN -> CH3CH2CN + KBr
Useful for extending carbon chains. Helps synthesise more complex compounds.

Question 5

Making primary amines

Answer 5

RX —NH3/heat in sealed tube-> RNH2
Heat RX w/ ammonia solution to make primary amine. Sealed tube prevents gas escaping. Nucleophile: NH3 molecule. Example 1-iodobutane into butylamine:
CH3CH2CH2CH2I + NH3 -> CH3CH2CH2CH2NH3 + I-
CH3CH2CH2CH2NH3+ + I- + NH3 -> CH3CH2CH2CH2NH2 + NH4+I-