Introduction to aldehydes and ketones

Question 1

What is a carbonyl goup?

Answer 1

carbon = oxygen double bond

Question 2

What is the difference between aldehydes and ketones?

Answer 2

• aldehyde:
  
  • the carbon bonded to the oxygen has at least one hydrogen atom bonded to it
  • end of chain
  • general formula - RCHO
• • ketones:
    
    • the carbonyl carbon has two organic groups
    • middle of chain
    • RR’CO

Question 3

How are aldehydes and ketones named?

Answer 3

aldehyde use the suffix -al

an aldehyde group can only occur at the end of a chain, so a numbering system is not needed to show its location

ketones use the suffix -one

no ketyones with fewer than three carbon atoms are possible, as the ketones must have two carbon atoms bonded to the carbonyl carbon

numbers aren’t need in propanone or butanone as the carbonyl group can only take one position

Question 4

How do boiling points of carbonyl compounds compare to tho of alkanes with a comparable molecular mass?

Answer 4

carbonyl group is polar

there are strong permanent dipole-dipole forces between all molecules

higher boiling points that alkanes

not as high as alcohol

Question 5

Are carbonyl compound soluble?

Answer 5

shorter chain carbonyl compound mix completely with water because hydrogen bonds form between the oxygen of the carbonyl compound and the water

solubility decreases with increasing chain length

Question 6

Are carbonyl compounds very reactive?

Answer 6

The C=O bond is strong

although almost all reactions involve the C=O bond

Question 7

Explain this reactivity?

Answer 7

because the bond is strongly polar due to a big difference in electronegativity

so nucleophillic reagents attack the partially positive carbon

since they contain a double bond, carbonyl compounds are unsaturated and addition reaction are possible