Predicting Physical Properties of Molecules from Functional Groups

Learning outcomes

• To become familiar with identifying key functional groups within molecules.

• To be able to explain the influence of functional groups on intermolecular forces.

• To be able to predict the physical properties of molecules from functional groups present.

Butanoic acid has a powerful, unpleasant odour. It is found in rancid butter, Parmesan cheese and vomit.

Can you identify and name the functional group present in butanoic acid?

Carboxyl group

Aqueous solutions of methanal are commonly used in embalming to preserve human or animal remains.

Can you identify and name the functional group present in methanal?

Carbonyl group

Is methanal an aldehyde or a ketone? Aldehyde

The molecule below is found in the disinfectant Dettol, which we instantly recognise by its distinctive smell. Dettol (chloroxylenol) helps us fight unwanted bacteria.

Can you identify and name the functional group present in Dettol?

Hydroxyl group

Carboxyl group

Amide group

4-formamidobenzoic acid is used in pharmaceutical compositions.

Can you identify and name two functional groups present on the 4-formamidobenzoic acid molecule?

Cinnamon is a tasty spice used to flavour biscuits, cakes and pies. Cinnamon also has medicinal properties.

Can you identify and name two functional groups in cinnamon?Is cinnamon an aldehyde or a ketone?

Carbonyl group

Carbon-to-carbon double bond

Aldehyde

What is the strongest type of intermolecular force of attraction between cinnamon molecules?

(Hint: Think about the bond polarity of the functional groups present!)

Can you identify and name the two functional groups present in methyl anthranilate?

Amino group

Methyl anthranilate occurs naturally in grapes and is used as grape flavouring in drinks and chewing gum.

Ester link

Can you identify and name three different types of functional group on the structure of vitamin C?

Ester link

Hydroxylgroup

Vitamin C is needed in your diet for the growth and repair of tissues in all parts of your body.

Carbon-to-carbon double bond

Which is the strongest type of intermolecular force of attraction between molecules of vitamin C?

Is vitamin C a polar or a non-polar molecule?

Is vitamin C soluble in water or in hexane?

(Hint: Think about which functional groups are present!)

Glucose is a simple sugar that is used as an energy source by many living organisms.

Is glucose soluble in water or in hexane? Justify your answer with reference to the functional groups present.

2-methylpropane is a branched hydrocarbon that is used as a refrigerant.

Is 2-methylpropane soluble in water or in hexane? Justify your answer with reference to the structure.