The molecular and crystal structure of trimethylamine oxide, (CH3)3NO

Abstract

Crystals of (CHs)aNO are monoclinic, space group C2/m, 4 molecules in a unit cell with lattice constants a = 10.054, b = 8.793, c = 5.006 A and fl = 91.04 °. The required molecular symmetry is m. Fourier and least-squares refinement on 514 visually estimated intensities were used to obtain optimum values for 23 positional and 23 thermal parameters. The value of R is 7.4%. The bond distances found are (values including the libration correction are given in parentheses): N-O = 1.388_+0.005 (1.404), average C-N=1.477 _+0.006 (1.495), and average C-H=I.01 _+0.07 /~. The bond angles at the nitrogen atom are O-N-C = 110.0 _+ 0.6 ° and average C-N-C = 109.0 +0-6 °. The C-N and N-O bond distances are compared with those in other compounds.

The molecular and crystal structure of 8-hydroxyquinoline N-oxide

“…There appears to be an inverse relationship between the N-O and O... O bond lengths as given in the Table.* This trend is reasonable if the O...O bond lengths are at all indicative of hydrogen bond strength, since a stronger hydrogen bond will delocalize the electrons on the N-oxide oxygen atom more than a weak hydrogen bond. This is also consistent with the theory of Caron, Palenik, Goldish & Donohue (1964) that a decrease in one of the formal charges across the N-O bond will result in an increase in bond length.…”

9-[3-(Dimethyloxyamino)propylimino]-1-nitro-9,10-dihydroacridine monohydrate

“…The unusual N(22)+-O(25) -bond is 1.37/i,, similar to that found in trimethylamine oxide by Caron, Palenik, Goldish & Donohue (1964).…”

The crystal structure of pyridine 1-oxide

“…The carbon-nitrogen bond length is equal to 1-34 A, the average for conjugated heterocyclic systems (Sutton, 1965). The N-O bond length (1.35/~) in 1-oxide is somewhat shorter than the 1.388 "pA yridinefor the N-O length in trimethylamine oxide (Caron, Palenik, Goldish & Donohue, 1964) (Eichhorn, 1959(Eichhorn, , 1956). In the latter, the C(2)-C(3) distance is 0.04 N less and the N-O distance 0.09 A less than in pyridine 1-oxide.…”

“…The screw axis produces an alternation of the dipole moment directions and minimizes the dipole-dipole interactions in a given stack. Trimethylamine N-oxide (Caron, Palenik, Goldish & Donohue, 1964), which has a dipole moment larger than that of pyridine 1-oxide, exhibits alternation of dipole orientation in directions parallel to each of the three crystallographic axes. The relative compactness of trimethylamine N-oxide permits molecules related by the twofold screw to be separated by only 4.5 A, which is quite a bit smaller than c/2 (6.9 A) for pyridine 1-oxide.…”