DF - isomerism

Question 1

General formula

Answer 1

a formula that can describe any member of a family of compounds

eg. CnH2n+1OH for alcohols

Question 2

Molecular formula

Answer 2

the actual no. of atoms of each element in a molecule

eg. C2H10O

Question 3

Shortened structural formula

Answer 3

shows the atoms, carbon by carbon, with the attached hydrogens and functional groups

Question 4

Structural formula

Answer 4

shows how all the atoms are arranged and all the bond between them

Question 5

Skeletal formula

Answer 5

shows the bonds of the carbon skeleton only, with any functional groups

the hydrogen and carbon atoms are not shown

Question 6

what is structural isomerism?

Answer 6

structural isomers have a different structural arrangement of atoms
- the atoms are connected in different ways but still have the same molecular formula

Question 7

what are the 3 types of structural isomers?

Answer 7

1. different carbon skeleton
2. functional group in different place
3. different functional groups

Question 8

different carbon skeleton - explain and effects

Answer 8

the carbon skeleton can be arranged differently
eg. as a straight chain or branched - butane and methylpropane

have similar chemical properties but physical properties, like boiling point, will be different because of the change of shape in the molecule

Question 9

functional group in different place - explain and effects

Answer 9

the skeleton and functional group could be the same only with the functional group attached to a different carbon atom
eg. butan-1-ol and butan-2-ol

different physical properties and the chemical properties might be different too
eg. primary, secondary and tertiary alcohols

Question 10

different functional groups - explain and effects

Answer 10

the same atoms can be arranged into different functional groups
eg. butan-1-ol and ethoxyethane

they will have very different physical and chemical properties

Question 11

Is there rotation around C=C double bonds?

Answer 11

No

doubles bonds are rigid and don’t bend much either

Question 12

Is there rotation around C-C single bonds?

Answer 12

Yes

C-C bonds rotate freely - like wheels on an axis

Question 13

What is Stereoisomerism?

Answer 13

Stereoisomers have the same shortened structural formula but a different arrangement in space

Question 14

What causes stereoisomerism?

Answer 14

the lack of free rotation around the C=C double bond

Question 15

What are the types of stereoisomerism? - explain them

Answer 15

Z-isomers and E-isomers

1. Z-isomers (cis) - the same side, the hydrogens are either both below or both above the plane
2. E-isomers (trans) - across, the hydrogens are not on the same side

if no hydrogens - cis/trans is used, looks for the same groups.