Carbonyl chemistry - OCR GCE Chemistry A Level

In the balanced equation for aldehyde oxidation, how many moles of water are produced per mole of aldehyde?

• 0

• 0.5

• 1

• 2

Answer explanation

An oxygen atom is inserted into the aldehyde group, and that is all.

Since there's no change in the number of Hs, there is no need for water production.

How many carbonyl groups are there, in total?

(a)  

Answer explanation

Only aldehydes and ketones are carbonyls.

Carboxylic acid and ester functional groups do not count: they have very different chemistry.

Which is the correct structural formula for ethanal?

• CH₃COOH

• CH₃COH

• CH₃CHO

• CH₃COCH₃

Answer explanation

COH is a tertiary alcohol group

Which show correct skeletal formulae?

• a

• b

• c

• d

Answer explanation

In OCR, we never display C-H bonds in a skeletal formula.

(At university a lot of people do!)

Name (d)

(a)  

Name (c)

(a)  

Answer explanation

The ketone group can only go on carbon number 2, so we wouldn't bother writing butan-2-one

Which compounds are chemically implausible?

• a

• b

• c

• d

Answer explanation

Aldehyde functional groups (CHO) must go at the end of a chain (or on a branch) - not in the middle of a chain.

Name (c)

(a)  

Answer explanation

Remember to count the C=O carbon

Name the compound

(a)  

Answer explanation

Ketone is highest priority functional group, so the suffix is -one

Number the carbons such that the highest priority group has the lowest number possible

Remember hyphens between numbers and letters

Name the compound

(a)  

Answer explanation

Identify alkene groups by replacing 'an' in the name with '-x-en', where x is the lowest number C on the C=C group.