Structured response question -SL001

1.a) Given the structures of the repeating units of the polymers below, identify the monomers from which they are formed:

i) -(CH2-CH2)-

 ans (i)
The structure shown is that of poly(ethene). This is an addition polymer formed from addition of ethene monomers, CH2=CH1.

ii) -(CO-CH(CH3)-NH)-
 ans (ii)

The two 'ends' of the polymer repeating unit show that the polymer is held together by amide, -CONH-, linkages. The monomer must therefore have had both an amine and a carboxylic acid 'end'.

The monomer is HOOC-CH(CH3)-NH2

iii) -(-NH-(CH2)6-NH-CO-(CH2)4-CO-)-
ans (iii)

The polymer has two different hydrocarbon chains joined by an amide linkage. This must have come from two separate monomers, each having two functional groups.

The monomer that gives the left hand side of the repeating polymeric unit is NH2-(CH2)6-NH2

The monomer that gives the right hand side of the repeating polymeric unit is HOOC-(CH2)4-COOH

  b) Describe the essential differences between the structures of monomers that form addition polymers and the structures of monomers that form condensation polymers.
 ans (b)
Monomers that form addition polymers must have a double bond. Condensation polymers come from monomers that have functional groups able to join together by means of a condensation reaction.

  c) Many organic compounds can exist as isomers. Draw and name an isomer of ethanoic acid CH3COOH
 ans (c)

Isomers have the same molecular formula but a different structural arrangement of the atoms. CH3COOH can be rearranged into:

CH(OH)=CH(OH), ethene-1,2-diol, or CH2(OH)CHO, hydroxyethanal

  d) Give the structural formulas for the isomers of molecular formula C4H10 and state the name of each one.
 ans (d)

Structural isomers have a different arrangement of the atoms in the formula. C4H10 has two isomers: