Adenine Abundance in a Collapsing Molecular Cloud

A vital ingredient of DNA molecule named adenine may be produced by successive addition of HCN during molecular cloud collapse and star formation. We compute its abundance in a collapsing cloud as a function of the reaction rate and show that in much of the circumstances the resulting amount may be sufficient to contaminate planets, comets and meteorites. We introduce a $f$-parameter which may be used to study the abundance where radiative association takes place.