optical isomers aldehyde and ketones

Question 1

what is a structural isomer
and what are the 3 types of them

Answer 1

same molecular formula
different structural formula

chain isomerism
positional isomerism
functional group isomerism

Question 2

what is the defiention of stereoisomers and the 2 types

Answer 2

same structural formula
different physical position in space

geometrical isomerism (E/Z)
optical isomerism

Question 3

optical isomerism
when does it occur ?

Answer 3

when a carbon atom bonds to four DIFFERENT groups

Question 4

optical isomers are __________ mirror images

Answer 4

non-superimposable

Question 5

what is an optical isomers

Answer 5

rotate the plane polarised light
one isomer rotate it clockwise and the other will rotate it anti-clockwise

Question 6

chiral

Answer 6

a molecule which can exists as a pair of optical isomers is chiral

Question 7

chiral centre

Answer 7

carbon is attached to 4 diffrent groups

other names - stereogenic centre/ asymmetric carbon

Question 8

enantiomer

Answer 8

one optical isomer out of the pair

Question 9

enantiomerically pure

Answer 9

a sample that only contains one optical isomer

Question 10

optically active

Answer 10

enantiomerically pure compound is optically active as it will rotate the plane of polarised light (in one direction only)

Question 11

racemic mixture

Answer 11

equal quantities of enantiomers

Question 12

what similar properties will optical isomers have

Answer 12

melting point
boiling point
mr
solubility

Question 13

reduction of aldehydes and ketones to alcohols using NaBH4
reagent, mechanism name, nucleophile, condition

Answer 13

reagent: NaBH4 then HCL
mechanism: nuclephillic addition
nucleophile: :H- (hydride ion)
condition: acidic solvent needed

Question 14

addition of hydrogen cynaide to aldehydes and ketones reaction

reagent, mechanism, nucleophile, condition, name of product

Answer 14

reagent: KCN then HCL
mechanism: nuclephillic addition
nucleophile: -:CN
condition: acidic solvent needed
name of product: hydroxy nitrile

Question 15

why can nucleophilic addition to aldehydes and asymmetrical ketones result in a racemic mixture of optical isomers?

Answer 15

the bonding about a R-C=O group in an aldehyde and ketone is planar

this means there is a 50:50 chance of the nucleophile attacking from one side of the molecule or the other

this results in equal proportions of each optical isomer forming, and so a racemic mixture is formed