What is the molecular structure of wood?
Wood is not a pure compound, it is a mixture of various substances.....
Like other vegetation, wood is cellular in structure. The walls of the cells are made of a mixture of cellulose and hemicellulose (40 - 50% cellulose, 15 - 25% hemi) and these are impregnated with 15-30% of the substance known as lignin.
Cellulose is a crystalline polysaccharide whilst hemicellulose is a more amorphous analogue of cellulose. Polysaccharides are basically polymers of sugars. Lignin is a complex biopolymer; you can see the structure of lignin here http://www.biomass-chemistry.com/research-development/linear-structure-lignin/structure-lignin.html