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Organic Chemistry Year 2 > Optical isomerism > Flashcards

Flashcards in Optical isomerism Deck (16)
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1

what property must a carbon have for the molecule to display optical isomerism about that carbon atom

4 different substituents attached to one carbon atom

2

what are the similarities and differences between two optical isomers

same atoms and bonds, but they are not superimposable mirror images of one another. not identical in chemical properties necessarily.
differ in the way they rotate plane polarised light- rotate plane of polarisation by the same angle but in different directions.

3

what word is used to describe optically active molecules

chiral

4

what are the pair of isomers called

enantiomers

5

what is the chiral centre

the carbon that has four different substituents attached to it

6

how is the chiral centre denoted

C*

7

How is light polarised

by passing it through a polarised filter, so oscillations are only in one plane

8

what effect does the racemix mixture have on plane polarised light

none

9

what effect does the + isomer have on plane polarised light

rotates plane of polarisation by X' clockwise

10

what is the structure of a polarimeter

light source
polarising filter
polarised light passes through compartment containing sample
detector determines the angle of rotation of the plane polarised light

11

what are polarimeters used fore

to identify which enantiomer is present
the purity of the sample
the concentration of the sample

12

first reaction of the synthesis of lactic acid from ethanal

CH3CHO + HCN -> CH3CH(OH)CN

13

second reaction of the synthesis of lactic acid from ethanal

CH3CH(OH)CN + HCL + 2H2O -> CH3CH(OH)COOH + NH4CL

14

are racemic mixtures formed in nature

not often, as enzyme mechanisms are 3D so only form one enantiomer

15

why is optical isomerism a problem for the drug industry

sometimes, only one enantiomer is effective due to enzyme's active/cell receptors being 3D

16

what are the options to resolve the issue of only one enantiomer being effective

separate enantiomers- difficult and expensive as have similar properties
sell racemate- wasteful as half is inactive
design alternative synthesis to only produce one enantiomer