Alkenes

Question 1

why are alkenes more reactive than allanes

Answer 1

they have a c=c bond which is a region of high electron density

Question 2

what is the name of an electron deficient species

Answer 2

electrophile (electron pair acceptor)

Question 3

what happens when alkenes react with hydrogen halide (electrophillic addition)

and what conditions

Answer 3

alkenes react with hydrogen halide in the GAS PHASE or in CONCENTRATED AQEUOS SOLOUTION to form halogenoalkanes

Question 4

what happens when alkenes react with bromine water

Answer 4

when alkenes are added to bromine water, a red-brown colour is decolourised

this shows the presence of carbon-carbon double bond

this is used to test for alkenes

Question 5

how can bromine water act as an elecrrophile if it is non polar

Answer 5

because the electron rich area of the double bond induces a dipole on the bromine molecule

Question 6

what happens when alkenes react with sulphuric acid

Answer 6

when alkenes are absorbed by COLD , CONCENTRATED SULPHURIC ACID . alkyl hydrogensulphates are formed

Question 7

how many products are formed with symmetrical alkenes with HBr or H2SO4

Answer 7

1

Question 8

how many products are formed with unsymmetrical alkenes with HBr or H2SO4

Answer 8

can lead to formation of 2 different products

a major product
and
a minor product

Question 9

which carbocation is most stable ? primary secondary or tertiary

Answer 9

tertiary

Question 10

what is PVC

Answer 10

poly(chloroethene)

Question 11

what is pure poly(chloroethene) typically like and why

Answer 11

hard and rigid because of permanent dipole dipole forces between chains due to €+ C and $-Cl

Question 12

what is added to poly(chloroethene) to make it more flexible and reduce the effectiveness of the permanent dipole dipole forces

what is the most common plasticiser

Answer 12

plasticisers to make it more flexible

phthalates