  Recently interest in GUT baryogenesis has been resurrected due to the
observation that B-violating dimension seven operators that arise in grand
unified theories that also violate B-L produce baryon asymmetry that cannot be
wiped out by sphaleron processes. While a general analysis of such higher
dimensional operators from a bottom up approach exists in the literature, a
full analysis of them derived from grand unification does not exist. In this
work we present a complete analysis of B-L=-2 operators within a realistic
SO(10) grand unification where the doublet-triplet splitting is automatic via a
missing partner mechanism. Specifically we compute all allowed dimension five,
dimension seven and dimension nine operators arising from matter-Higgs
interactions. The relative strength of all the allowed B-L=-2 operators is
given. Such interactions are useful in the study of neutrino masses,
baryogenesis, proton decay and $n-\bar n$ oscillations within a common
realistic grand unification framework.
