Organic chemistry 3 (13)

Question 1

What is isomerism ?

Answer 1

Molecules which have the same molecular formula, but differ in the arrangement of their atoms,

Question 2

What are structural/constitutional isomers ?

Answer 2

Structural (aka constitutional) isomers differ in their bonding sequence/molecular skeleton.

Question 3

What are stereoisomers ?

Answer 3

Stereoisomers differ only in the arrangement of the atoms in space

Question 4

What are structural isomers ?

Answer 4

Structural isomers are usually different compounds with different physical and chemical properties

Question 5

Describe chain/skeletal isomerism

Answer 5

Difference in vcarbon skeleton

Question 6

Describe Position isomerism

Answer 6

Different position of the functional group

Question 7

Describe Functional isomerism

Answer 7

Different identity of the functional group

Question 8

Describe Tautomerism isomerism

Answer 8

Different movement of bonds and a proton

Question 9

What are sterioisomers ?

Name two

Answer 9

Same structural formula but different 3-D arrangement of atoms in space

2 Types:
Geometric (cis-trans; E/Z) Isomerism
Optical Isomerism

Question 10

What `causes geometric isomerism

Answer 10

restricted rotation around a bond

Requires different groups at each end of the bond

Question 11

What bonds restrict rotation around a bond ?

Answer 11

Double (pi) bond – rotation breaks the bond = not allowed without energy input

Question 12

Name two types of geometric isomers

Answer 12

Cis and trans
Or
E and Z (which is the systematic name )

Question 13

How can you distinguish between cis and trans isomers ?

Answer 13

Cis isomer – two alkyl groups are on the same side of the double bond

Trans isomer – two alkyl groups are on the opposite side of the double bond

Question 14

Define dextrorotatory

Answer 14

A d-isomer or +-isomer that rotates the plane polarised light to the right (clockwise)

Question 15

Define laevorotatory

Answer 15

l-isomer or (-tive)-isomer Is a compound that rotates the plane of polarised light to the left (anticlockwise) known as laevorotatory: l-isomer or (–)-isomer

Question 16

What is a chiral centre ?

Aka asymmetric

Answer 16

A carbon atom bonded to four different substituents lacks a plane of symmetry

Question 17

What is the major fisher rule ?

Answer 17

Carbon chain is on the vertical line . And rotation of 180 doesn’t change the plane of the molecule

Question 18

What are enantiomers ?

Answer 18

non-superimposable mirror image forms of a chiral molecule

They represents two optical isomers: (+) and (-)
Their opposite rotatory powers are due to the opposite arrangements of groups around each asymmetric carbon atom.

Question 19

How are enantiomers different ?

Answer 19

Non-superimposable mirror images of each other
In the way they rotate the plane of polarised light
Their interaction with chiral molecules

Question 20

What us a race if mixture ?

Answer 20

A 1:1 mixture of the two enantiomers of a compound
That has no optical activity
And many have a different bp or mo from the enantiomers

Question 21

How many isomers can a compound with 6 chiral centres have ?

Answer 21

Two to the power of 6

Which is 64

Question 22

What are diasteromers ?

Answer 22

Stereoisomers that’s re not mirror images of each other