Organic Chemistry 3.1 - Stereo Chemistry - Optical Isomers

Question 1

What are isomers?

Answer 1

compounds with the same molecular formula, but different structural formula

Question 2

Isomers are compounds with the same ___ formula, but different ___ formula

Answer 2

molecular, structural

Question 3

Name the different types of isomers please

Answer 3

1. Structural isomers (higher)
2. Stereoisomers (optical and geometric)

Question 4

What are structural isomers?

Answer 4

compounds with the same atoms, but bonded together in a different order
(eg butane and 2-methylpropane)

Question 5

What are stereoisomers?

Answer 5

Stereoisomers are compounds with bonding between atoms in exactly the same order, but a different spatial arrangement. (eg left hand right hand)

Question 6

Stereoisomers are compounds with ___ between ___ in exactly the same order, but a different ___ ___.

Answer 6

bonding, atoms, spatial arrangement

Question 7

What is an optical isomer?

Answer 7

when a molecule’s mirror image is non-superimposable

Question 8

An optical isomer is when a molecule’s ___ image is…

Answer 8

mirror, non-superimposable

Question 9

A molecule that is non-superimposable is said to be…

Answer 9

chiral. (distinguishable from it’s partner, asymmetrical)

Question 10

Mirror images can be ___, or ___.

Answer 10

identical or different.

Question 11

Optical isomers exist for compounds with…

Answer 11

four different atoms/groups arranged tetrahedrally around a carbon atom.

Question 12

A pair of optical isomers are described as ___.

Answer 12

enantomers

Question 13

A 50/50 mixture of two enantomers is called a…

Answer 13

racemic mixture

Question 14

What are enantomers?

Answer 14

a pair of optical isomers (‘optically active molecules’)

Question 15

What is a racemic mixture?

Answer 15

an even (50/50) mixture of two enantomers

Question 16

When a carbon has four different groups attached, it is described as ___.

Answer 16

chiral

Question 17

Normal light vibrates in ___ ___.
Plane-polarised light vibrates in ___ ___.

Answer 17

all directions.
one direction

Question 18

How can plane-polarised light be produced?

Answer 18

passing light through a polarised filter

Question 19

What affect do (a pair of) enantomers have on plane polarised light?

Answer 19

The two molecules rotate plane polarised light by the same degree, but in opposite directions

Question 20

A substance is said to be optically active if…

Answer 20

it can rotate a plane of polarised light

Question 21

Are racemic mixtures optically active?
Why?

Answer 21

no.
because the opposite rotations of a plane of light cancel each other out

Question 22

In which two ways do enantomers act differently?

Answer 22

when rotating plane polarised light,
and when in a chiral environment (eg a biological system)

Question 23

Chiral molecules react differently with other ___ ___.

Answer 23

chiral molecules

Question 24

Enantomers have ___ chemical properties, except when in a ___ environment, such as a ___ system.

Answer 24

identical, chiral, biological

Question 25

Different enantomers can have different effects on…

Answer 25

the body

Question 26

Give an example of something with an identical mirror image, and something with a non superimposable mirror image.

Answer 26

A pencil
your hands