week 5

Question 1

The Carbonyl Group

hyridsation

polarised +?

Answer 1

• A carbonyl is a double bond between an sp2 carbon and an sp2 oxygen
  • It is made of a σ-bond (between sp2 orbitals) and a π-bond (between p orbitals).
  • It is polarised due to the difference in electronegativity between carbon and oxygen (more details to follow).
    aldehydes and ketones

Question 2

Aldehydes and ketones

Answer 2

The aldehyde functional group consists of a carbonyl centre with a hydrogen and a hydrocarbon group (alkyl) attached (Figure 2).

Question 2

A ketone functional group

Answer 2

consists of a carbonyl center with two hydrocarbon groups (alkyl) attached (Figure 3).

Question 2

Electronegativity in carbonyl

Answer 2

Electronegativity is a measure of the tendency of an atom to attract electrons
oxygen is more electronegative than carbon.

Question 3

hybridization of carbonyl oxygen in aldehyde

Answer 3

the same process occurs and in this case two of the sp2 hybrid orbitals contain lone pairs of electrons.

The carbon atom and the oxygen atom then bond much like in the example of ethene, with end-to-end overlap of the atomic orbitals that are pointing towards one another (Figure 5) to produce a σ-bond.

This leaves the p-orbitals to overlap sideways producing a π-bond.

Question 3

hybridization of carbonyl carbon in aldehyde

bond angle
times of bonds

Answer 3

carbonyl atom are sp2 hybridized. The electrons of the carbon atom rearrange themselves to give three sp2 hybrid orbitals that are 120° to each other. The remaining p-orbital is at right angles to the hybrid orbitals.

Question 4

grinard reagent

Answer 4

add carbonyls to give alcohol

Question 5

Synthesis of alcohols

Answer 5

The hydration of aldehydes
ketones and esters is a common way to make alcohols

This addition reaction is with ctatylsst and water

The hydration reaction follows the same rules (Markovnikov, for example) as the addition of H-X to an alkene.

Question 6

Oxidation of alcohols

Answer 6

• Primary alcohols have two C-H bonds. They are oxidised first to the aldehyde. The aldehyde has a remaining C-H bond and can be further oxidised to the carboxylic acid.
  • Secondary alcohols have one C-H bond. They are oxidised to the ketone.

Tertiary alcohols have no C-H bonds, and can not be oxidised to a carbonyl compound.