MOD 4- Alkenes

Question 1

Describe the bonding in alkenes

Answer 1

Double covalent bond is made of a

Sigma bonds- overalp of electron clouds

Pi bond- electrons in adjacent p-orbitals overlapping above and below the carbon atoms. This can form only after a sigma bond

Question 2

Which bond restricts rotation

Answer 2

Pi bonds restrict rotation.

Question 3

Geometric isomers-Cis/Trans isomers rules

Answer 3

Only occur around double C=C bond
2 different groups attached to each carbon atom in the double bond
Each carbon is attached to the same group.

Question 4

____________ have a fixed arrangement since thee is no _________ __________ so no reaction takes place

Answer 4

Alkanes have a fixed arrangement since there is no double bonds so no reaction takes place

Question 5

Priority and Z isomerism

Answer 5

If 2 high priority groups are on the same side of the double bond it is an E isomer.

Question 6

Bond enthalpy of C=C bond
C-C

Answer 6

C=C - 612 kJmol-1
C-C - 347 kJmol-1

Question 7

Bond enthalpy of the pi bond is ______ kJmol-1. The pi bond is weaker than the sigma bond and is therefore more easily broken.

Answer 7

Bond enthalpy of the pi bond is weaker than the sigma bond and is therefore more easily broken

Question 8

Define markownikoffs rule

Answer 8

Where a hydrogen halide reacts with an unsymmetrical alkene, the hydrogen of the hydrogen halide attaches itself to the carbon atom of the alkene with the greatest number of hydrogen atoms and small number of carbon atoms.

Question 9

Define addition polymerisation

Answer 9

Formation of long chains molecules from lots of small molecules joining together with no other products.

Question 10

Define addition reactions

Answer 10

A small molecule across the double bond causing pi bond to break and for new bonds to form

Question 11

Define addition reactions

Answer 11

A small molecule across the double bond causing pi bond to break and for new bonds to form