Dipole Moment of Formic Acid, HCOOH and HCOOD

The magnitude and the direction of the dipole moment of formic acid were determined through the Stark effect of rotational transitions. The dipole moments of HCOOH and HCOOD are 1.415±0.01 D and 1.39±0.01 D, respectively. The direction of the dipole moment lies between C–H and C=O bonds making an angle of 42.4°±2° with the C=O bond.