Describe the classification of polymers on the basis of structure.

OR

(i) Write the product obtained when D-Glucose reacts with HCN.

(ii) What type of bonding stabilises the alpha helix structure of proteins?

(iii) Write the name of the disease caused by the deficiency of Vitamin B₁₂.

• Polymers can be classified into three main types based on structure. These are linear polymers, branched chain polymers and cross- linking polymers.

• Linear polymers are formed of long, straight chains. Examples of this type include high density polythene (HDP), polyvinyl chloride etc.

• Branched chain polymers contain of linear chains having branches. Some examples include low density polythene etc.

• Cross linking polymers are also called network polymers and are usually formed from bi-functional and tri-functional monomers.

• These contain very strong covalent bonds between various linear polymer chains. Examples of cross-inking polymers include Bakelite, Melamine formaldehyde resin etc.

OR

(i)

• The addition of HCN to D-Glucose leads to the formation of D-Gluconitrile and D-Mannononitrile.

• The addition of cyanide to the aldehyde group lengthens the glucose chain by 1 atom which generates a new stereo centre through which 2 configurations are possible.

• The structures of the produced compounds are as follows

(ii)

• One of the secondary structures of proteins is and alpha helix structure.

• The stability of this structure is attributed to the hydrogen bonding between the hydrogen of the amino group of the n^th amino acid and the oxygen of the carbonyl group of the (n+4)^th amino acid.

(iii)

• The main deficiency caused by lack of Vitamin B₁₂ is Beri-Beri.

• A person suffering from Vitamin B₁₂ deficiency suffers from loss of appetite and retarded growth.