Basic Organic Chemistry and Isomerism

Question 1

What is the general formula for a compound?

Answer 1

An algebraic formula which can decribe any member from a family of compounds (i.e. C_nH_2nfor alkenes).

Question 2

What is the empirical formula for a compound?

Answer 2

The simplest whole-number ratio of atoms of each element in a compound.

Question 3

What is the molecular formula for a compound?

Answer 3

The actual number of atoms of each element, with any functional groups indicated (i.e. C₂H₅OH).

Question 4

What is the structural formula for a compound?

Answer 4

The formula which shows the molecule carbon-by-carbon (i.e. CH₃CH₂COOH).

Question 5

What is the displayed formula for a compound?

Answer 5

The formula which shows how the atoms in that compound are arranged and the bonds between those atoms.

Question 6

What is the skeletal formula for a compound?

Answer 6

The skeletal formula only shows the carbon chain, with any functional groups indicated.

Question 7

The defining feature of structural isomers is…?

Answer 7

A different structural arrangement.

Question 8

The defining feature of stereoisomers is…?

Answer 8

Different spatial arrangements.

Question 9

What are the three types of structural isomerism?

Answer 9

Positional (different functional group position), chain (different main chain length), and functional (different functional group).

Question 10

What do double bonds create in terms of isomerism?

Answer 10

Geometrical isomers - double bonds restrict rotation, meaning that the molecules are in a fixed arrangement about each carbon involved in the double bond.

Question 11

What is the meaning of ‘entgegen’?

Answer 11

‘Opposite’

Question 12

What is the meaning of ‘zusammen’?

Answer 12

‘Together’

Question 13

What is an enantiomer?

Answer 13

An optical isomer - isomers which are mirror images of one another and cannot be superimposed over one another, regardless of their orientation.

Question 14

What is the key feature of optical isomers?

Answer 14

A chiral carbon atom - a carbon which is bonded to four different groups.

Question 15

How can enantiomers be distinguished from one another?

Answer 15

They rotate plane-polarised light in opposite directions.

Question 16

What is a racemate?

Answer 16

A mixture of equal quantities of optical isomers of one compound.

Question 17

Why do achiral compounds react to produce racemic mixtures?

Answer 17

Because there is an equal chance of each enantiomer forming in reaction.

Question 18

Why is it that an apparently harmless enantiomer could cause damage to the human body?

Answer 18

Because the body is sometimes able to convert the harmless enantiomer into its harmful enantiomer - enantiomers can have different biological effects.