Structure of Formaldoxime

Abstract

The microwave spectra of cis‐CHDNOH, trans‐CHDNOH, C¹³H₂NOH, CH₂N¹⁵OH, and CH₂NO¹⁸H were assigned. Together with the results of previous work on the normal species and CH₂NOD, the data give the following planar structure for formaldoxime: bond lengths in Å; CH_cis=1.085, CH_trans=1.086, C=N=1.276, NO=1.408, OH=0.956; bond angles; H_cisCN 121°46′, H_transCN 115°33′, CNO 110°12′, NOH 102°41′. The most significant feature of the structure is the difference between cis‐ and trans‐HCN bond angles. This ``tilt'' of the methylene group appears to be too large to be attributed to steric repulsion. The C=N and N–O bond lengths are consistent with the Schomaker—Stevenson relation if allowance for resonance is made.