Alkenes

explain why there is an attraction between a C=C double bond and Br2

C=C electron rich/ high electron density

Br-Br becomes polarised

(delta +) Br attracted to C=C

observation if bromine water was added to poly(chloroethene)

observation = no reaction/ yellow-orange

explanation = polymer is saturated (does not contain double bonds)

why a plasticiser added

makes it more flexible

explain why more of isomer E than isomer F is formed in this reaction

E is formed by a more stable carbocation

2(y) carbocation is more stable than 1(y) carbocation

correct statement about poly(chloroethene)

its brittleness is reduced by plasticisers

explain why the two products are formed in different amounts

major product formed via a tertiary carbocation intermediate

minor product formed via a secondary carbocation intermediate

tertiary carbocation is more stable than the secondary carbocation

correct statement about ethene

it burns in excess oxygen to produce carbon dioxide and water

But-1-ene reacts with a reagent of the form HY which reacts with but-1-ene

HBr

HCl

H2SO4

explain how three isomeric products are formed when HY reacts with but-1-ene

major product exists as a pair of enantiomers

the third isomer is 1-bromobutane (minor product)

because it is obtained via a primary carbocation