Question

Methylcellulose forms a gel at elevated temperature due to:
A) Increased hydrogen bonding among methylcellose molecules

B) Release of water of hydration leading to interaction among methylcellulose molecules

C) Increased amount of water that is trapped inside the gel

D) Hydrolysis of the methyl group leading to increased hydrogen bonding

T/F: The peculiar properties of water molecule are due to ability of water molecules to associate with each other linearly by H-bonding

Answer 1

1. Option A is the correct answer. Gel formation at elevated temperature by methycellulose is due to the formation of a three-dimensional network of physical cross-links between macromolecules of methylcellulose. This three dimensional network is formed due to two reasons: 1. Hydrophobic association of methoxyl substituents and 2. Formation of inter-chain hydrogen bonds involving unsubstituted primary hydroxyl groups accompanied by a conformational change in the polymer backbone.

2. The statement is false. Water molecules does not associate linearly because of the bond angle (104.5 degree) between two covalently attached hydrogen. The lone pair of electron present on oxygen repel both hydrogen and thus causes a distortion angle (104.5 degree). Due to this bond angle water molecules do not associate linearly.