  The paper presents evidence of a rather strong correlation of odd electrons
in the singlet state of graphene. Due to the correlation, the chemical
modification of graphene can be considered following a certain algorithmic
computational procedure. Originated due to the correlation and distributed over
the carbon atoms of graphene membrane with fraction numbers NDA, effectively
unpaired electrons lay the algorithm foundation. The highest NDA value points
to the target atom that enters a chemical reaction at the considered step.
Following the pointers, a stepwise design of polyderivatives can be performed.
Applied to the hydrogenation, the algorithmic design has exhibited that
graphene hydrogenation should be attributed to a highly complicated event,
whose final hydride products depend on a number of factors such as: 1) the
manner of the graphene membrane fixation; 2) the accessibility of the membrane
both sides to hydrogen; 3) the composition (molecular or atomic) of the
hydrogen. In general, the hydride formation is multimode in regards composition
and structure. Thus, the formation of 100% hydride with regular chairlike
hexagonal packing of CH units which can be attributed to graphane is possible
if only the graphene membrane is fixed over perimeter while its basal plane is
accessible to hydrogen atoms from both sides.
