Cellulose is linear chains of $$\beta$$-D-glucose molecules linked together by $$\beta$$-1, 4 glycosidic bonds. Cellulose has $$\beta$$-1, 4 linkage between $$\beta$$-D-glucose units. The cellulose is linear molecule.

IIT-JEE 2008 Paper 2 Offline Chemistry - Biomolecules Question 2 English Explanation 1

A general reaction of alcohol with acetic anhydride is :

IIT-JEE 2008 Paper 2 Offline Chemistry - Biomolecules Question 2 English Explanation 2

Acetic anhydride reacts with the alcoholic function group and converts the alcoholic function group into ester functional group. The $$-$$OH is known as an alcoholic functional group. The $$-$$OC(O)$$-$$ is known as an ester functional group.

During the conversion hydrogen of alcoholic group is replaced by CH$$_3$$CO$$-$$ group of acetic anhydride. The above reaction is known as acetylation because acetyl group CH$$_3$$CO$$-$$ is attaching with the reactant alcohol.

So, upon acetylation of cellulose with excess acetic anhydride/H$$_2$$SO$$_4$$ (catalytic) all the $$-$$OH group will convert into acetyl group.

As the cellulose contains a large number of glucose units but our product is triacetate. It means the alcohol group of three glucose units of cellulose is converted into acetyl group. As the acetic anhydride is in excess, all alcoholic groups of three glucose units of cellulose will convert into acetyl groups.

So, the structure of the product is

IIT-JEE 2008 Paper 2 Offline Chemistry - Biomolecules Question 2 English Explanation 3

	Column I		Column II
(A)	Orbital angular momentum of the electron in a hydrogen-like atomic orbital.	(P)	Principal quantum number
(B)	A hydrogen-like one-electron wave function obeying Pauli's principle.	(Q)	Azimuthal quantum number
(C)	Shape, size and orientation of hydrogen like atomic orbitals.	(R)	Magnetic quantum number
(D)	Probability density of electron at the nucleus in hydrogen-like atom.	(S)	Electron spin quantum number