1.2-1.3 Optical Isomers And Aldehyde And Ketones

Question 1

Define :
-Optical isomers
-chiral
-chiral centre/stereogenic

Answer 1

1)rotate plane of polarised light one isomer will rotate in opposite directions
2)a molecule with a pair of optical isomers
3)a C with 4 diff groups attached

Question 2

Define
-asymmetric carbon
-enantiomer
-enantiomerically pure
-optically active
-Racemic mixture

Answer 2

1) chiral centre molecule
2) each optical isomer
3) a sample containing 1 optical isomer only
4)enantiomererically pure sample can rotate plane of P.L. In 1 direction
5) mixture contains equal quantities of optical isomers

Question 3

1)Mechanisms from aldehyde to alcohols.
2)Reagents 3)nucleophile 4)conditions 5)products

Answer 3

1) Nucleophilic addition
2)NaBH4 then HCl
3)H-
4) acidic solvent
5) alcohols

Question 4

1) Draw mechanism from aldehyde to alcohols

Answer 4

1)arrow from H- to C attached = O
2) arrow from C=O bond do H+
3) O: pair and minus charge
4) a

Question 5

Outline mechanis for reaction from aldehyde/ketones with HCN.
2)reagents 3)conditions 4)products

Answer 5

1)nucleo addition
2)HCN then HCl
3)acidic solvent
4)hydroxyalkanenitrile

Question 6

Draw the mechanism from ketone to nitrile.

Answer 6

1)arrown from :CN- to C+ve partial charge
2) C positive to O negative charge
3) O — O bond and CN attached
4) arrow from -O: to H+

Question 7

How can nucleophic addition result in a racemic mixture.(3)

Answer 7

1)C=O bond is planar
2)50:50 chance of nucleophile attack from one side to another
3)equal amounts of each optical isomers forms, forming racemic mixture