Halogenoalkanes 2 (R-X)

Question 1

Name all the halogenoalkanes production methods.

Answer 1

1.Free radical substitution.
2.Electrophilic addition of halogen.
3.Electrophilic addition of hydrogen halide.
4.Nucleophilic substitution of alchols.

Question 2

Name the 5 halogenoalkanes reactions.

Answer 2

1.Halogenoalkane+OH-(aq)—>Alcohol+NaX.
2.Halogenoalkane+NH3(ethanol)—>Amine.
3.Halogenoalkane+KCN-(ethanol)—>Nitrile+KX.
4.Halogenoalkane+H2O—>Alcohol+HX.
5.Halogenoalkane+OH-(ethanol)—>Alkene+NaX+H2O

Question 3

SN1 mechanism: what class of halogenoalkanes follow it? and what is the intermediate step?

Answer 3

Tertiary halogenoalkanes and sometimes secondary halogenoalkanes. Carbocation.

Question 4

SN2 mechanism: what class of halogenoalkanes follow it? and what is the intermediate step?

Answer 4

Primary halogenoalkanes and sometimes secondary halogenoalkanes. Transition state.

Question 5

Why is the nucleophilic substitution with OH- ion faster than that with H2O?

Answer 5

OH- ion has a full negative charge while the oxygen in H2O has a partial negative charge.

Question 6

Why does R-I bonds hydrolyse 1st, then R-Br bonds, then R-Cl, then R-F bonds?

Answer 6

R-I bond length is highest so it will hydrolyse first as less energy is needed to break the bond.
R-F bond length is shortest so it will hydrolyse last as more energy is needed to break the bond.

Question 7

Write the halogenoalkane reaction with aqueous OH- ion, and conditions.

Answer 7

R−X+OH−-→R−OH+NaX (heat).

Question 8

Write the halogenoalkane reaction with ethanolic NH3 ion, and conditions.

Answer 8

R−X+NH3(ethanol)​→R−NH2​ (heat and pressure)

Question 9

Write the halogenoalkane reaction with ethanolic CN- ion, and conditions.

Answer 9

R−X+KCN(ethanol)−→R−CN+KX (heat and reflux).

Question 10

Write the halogenoalkane reaction with water, and conditions.

Answer 10

R−X+H2​O→R−OH+HX (heat and refulux, and drops of acid or alkali)

Question 11

Write the reaction of Alcohol with hydrogen chloride (halogenoalkane production method).

Answer 11

R−OH+HCl→R−Cl+H2​O.

Question 12

Write the reaction of Alcohol with hydrogen bromide (halogenoalkane production method).

Answer 12

R−OH+HBr→R−Br+H2​O.

Question 13

Write the reaction of Alcohol with hydrogen iodide (halogenoalkane production method).

Answer 13

R−OH+HI→R−I+H2​O.

Question 14

How do we produce HBr?

Answer 14

NaBr+H2SO4(l)/H3PO4(aq)—>HBr+NaHSO4

Question 15

How do we produce HI?

Answer 15

NaI+H3PO4(aq)—>HI

Question 16

Write the reaction of Alcohol with PCl3 (halogenoalkane production method).

Answer 16

R−OH+PCl3​(with heat)→R−Cl+H3PO3.

Question 17

Write the reaction of Alcohol with PCl5 (halogenoalkane production method).

Answer 17

R−OH+PCl5→R−Cl+POCl3+HCl.

Question 18

Write the reaction of Alcohol with SOCl2 (halogenoalkane production method).

Answer 18

R−OH+SOCl2→R−Cl+SO2+HCl.