title: Oxygen-initiated chain mechanism for hydride transfer between NADH and NAD+ models. Reaction of 1-benzyl-3-cyanoquinolinium ion with N-methyl-9,10-dihydroacridine in acetonitrile.
abstract: A reinvestigation of the formal hydride transfer reaction of 1-benzyl-3-cyanoquinolinium ion (BQCN(+)) with N-methyl-9,10-dihydroacridine (MAH) in acetonitrile (AN) confirmed that the reaction takes place in more than one step and revealed a new mechanism that had not previously been considered. These facts are unequivocally established on the basis of conventional pseudo-first-order kinetics. It was observed that even residual oxygen under glovebox conditions initiates a chain process leading to the same products and under some conditions is accompanied by a large increase in the apparent rate constant for product formation with time. The efficiency of the latter process, when reactions are carried out in AN with rigorous attempts to remove air, is low but appears to be much more pronounced when MAH is the reactant in large excess. On the other hand, the intentional presence of air in AN ([air] = half-saturated) leads to a much greater proportion of the chain pathway, which is still favored by high concentrations of MAH. The latter observation suggests that a reaction intermediate reacts with oxygen to initiate the chain process in which MAH participates. Kinetic studies at short times show that there is no kinetic isotope effect on the initial step in the reaction, which is the same for the two competing processes. Our observation of the chain pathway of an NADH model compound under aerobic conditions is likely to be of importance in similar biological processes where air is always present.
authors.affiliation: Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, USA.
authors.forename: Weifang
authors.initials: W
authors.lastname: Hao
authors.forename: Vernon D
authors.initials: VD
authors.lastname: Parker
mesh_terms: D000097:Acetonitriles / Q000737:chemistry*; D000166:Acridines / Q000737:chemistry*; D001593:Benzyl Compounds / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009243:NAD / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D011804:Quinolines / Q000737:chemistry*
chemical_list: C480177:1-benzyl-3-cyanoquinolinium; C480178:10-methyl-9,10-dihydroacridine; D000097:Acetonitriles; D000166:Acridines; D001593:Benzyl Compounds; D011804:Quinolines; D009243:NAD; D010100:Oxygen; C032159:acetonitrile