isomerism

Question 1

structural isomerism

Answer 1

same molecular formula but different structural formula
chain - length of c chain
position - position of functional group
functional group - type of functional group

Question 2

stereoisomerism

Answer 2

same structural and molecular formula but have different arrangement of atoms in space
e/z and optical isomerism

Question 3

how e/z isomers arise

Answer 3

each carbon has to be bound to 2 different groups in c=c bond
there is restricted rotation around the c=c bond

Question 4

e/z isomers

Answer 4

e isomers - higher priority on opposite sides
z isomers - higher priority on the same side

Question 5

optical isomerism key points

Answer 5

optical isomerism can occur when a carbon atom bonds to four different groups

carbon centre with 4 different groups bonded - chiral centre
forms 2 isomers - mirrors images
pair of enantiomers

Question 6

what is optical isomerism

Answer 6

optical isomerism rotate the plane of polarised light
one isomer will rotate it clockwise the other isomer will rotate it anti clockwise in opposite direction

Question 7

optically inactive

Answer 7

if both isomers present in a sample no rotation will be seen
as 1 rotates clockwise the other rotates anticlockwise by the same amount

Question 8

optical isomers will have a number of similar properties

Answer 8

-same mp and bp
-same solubility in a range of solvents
-same mr
-same peaks in their mr spectrums

Question 9

racemic mixture

Answer 9

a sample that has both optical isomers in equal amounts

Question 10

enantiomer

Answer 10

single optical isomer

Question 11

enantiomerically pure

Answer 11

a sample that has 1 optical isomer

Question 12

thalidomide

Answer 12

drug developed in 1950s to relieve morning sickness in pregnant women
R optical isomer had desired effect
S optical isomer thought to have no effect
so drug was given as a racemic mixture
S isomer caused physical defects in unborn baby

Question 13

when producing a new drug there are three options

Answer 13

-supply drug as racemic mixture
runs the risk of unwanted side effects caused by other isomer
even if theres no side effects half the drug is ineffective which is wasteful and inefficient

-make the drug as a racemic mixture then separate out the two isomers
challenging as isomers are similar and few methods are available to separate them

–find a method synthesis in which only one enantiomer is formed
challenging but many starting materials which come from plants form in nature as single enantiomers so using one of these can ensure only 1 enantiomer is formed