a level Alkenes

Question 1

what is the nature of the double bond?

Answer 1

a sigma bond surrounded by a pi bond

Question 2

what is a pi bond?

Answer 2

the overlap of two p orbitals

Question 3

what shape are alkenes and why?

Answer 3

trigonal planar
3 regions of e- density around each c atom
all in the same plane

Question 4

what are stereoisomers?

Answer 4

have the same structural formula but a different arrangement of atoms in space

Question 5

what conditions are required for E/Z isomerism?

Answer 5

a c=c double bond

different groups attached to each c of the double bond

Question 6

what is cis-trans isomerism?

Answer 6

where one of the groups on each carbon is hydrogen

Question 7

what is the Cahn-Inglod-Prelog rule?

Answer 7

what distinguishes E/Z isomers

Question 8

how do you determine an atoms priority?

Answer 8

highest atomic no.

Question 9

why are alkenes relatively reactive?

Answer 9

the pi bond breaks easily

Question 10

why does the pi bond break easily?

Answer 10

bond enthalpy is weaker

Question 11

what addition reactions do alkenes undergo?

Answer 11

hydrogenation
halogenation
hydrogen halides
steam

Question 12

what conditions for hydrogenation?

Answer 12

423K and nickel catalyst

Question 13

what conditions for halogenation?

Answer 13

none but adding bromine water tests for unsaturation

Question 14

what conditions for the addition of hydrogen halides?

Answer 14

room temperature

Question 15

what conditions for hydration?

Answer 15

phosphoric acid catalyst

Question 16

why does electrophilic addition occur?

Answer 16

the double bond is an area of high e- density

this attracts electrophiles

Question 17

what is an electrophile?

Answer 17

a small molecule that accepts an electron pair and is added across the double bond

Question 18

what is the electrophilic mechanism?

Answer 18

the positive dipole is attra