Alkenes

Question 1

R&C for preparation of alkenes by eliminating H2O

Answer 1

excess conc H2SO4/H3PO4, heat

Question 2

R&C for preparation of alkenes by eliminating HX

Answer 2

KOH/NaOH in ethanol, heat

Question 3

R&C for reduction/hydrogenation

Answer 3

H2(g), Ni catalyst, heat

Question 4

R&C for electrophilic addition of HX

Answer 4

HX(g), r.t.

-reactivity increases down the group due to the weaker bond strength

Question 5

what is Markovnikov’s rule

Answer 5

for alkenes with different attached groups, the major product is the one where the H in HX attaches to the C bonded to more H atoms

Question 6

R&C for electrophilic addition of X2

Answer 6

X2 in CCl4, r.t. and absence of UV light to prevent FRS on alkyl groups

obs: orange Br2 rapidly decolourises

-can be used as an unsaturation test

Question 7

R&C for electrophilic addition of X2 with nucleophilic solvent (H2O, NH3 etc.)

Answer 7

X2(aq), r.t.

Question 8

R&C for electrophilic addition of water (hydration)

Answer 8

1) conc H2SO4, cold
2) warm with water
OR
H3PO4, steam, high temp & pressure

Question 9

R&C for MILD oxidation (no oxidative cleavage)

Answer 9

KmnO4(aq), NaOH(aq)/H2SO4(aq), cold

• extra brown ppt formed if NaOH used

Question 10

R&C for oxidation with oxidative cleavage

Answer 10

KMnO4(aq), NaOH(aq), H2SO4(aq), heat

-brown ppt formed if NaOH used