Each residue is oriented 180° to the next with the chain synthesized two residues at a time. Although individual strand of cellulose are intrinsically no less hydrophilic, or no more hydrophobic, than some other soluble polysaccharides (such as amylose) this tendency to form crystals utilizing extensive hydrophobic interactions [1645] in addition to intra- and intermolecular hydrogen bonding makes it completely insoluble in normal aqueous solutions (although it is soluble in more exotic solvents such as aqueous N-methylmorpholine-N-oxide (NMNO, ~0.8 mol water/mol, then up to 30% by wt cellulose at 100 °C [1060]), CdO/ethylene-diamine (cadoxen), LiCl/N,N'-dimethylacetamide or near-supercritical water [1070]). It is thought that water molecules catalyze the formation of the natural cellulose crystals by helping to align the chains through hydrogen-bonded bridging.