Diwakar M. Pawar

Dynamic NMR studies of cyclopropyldifluoroborane and vinyldifluoroborane

Abstract The two fluorines of cyclopropyldifluoroborane ( 1 ) and vinyldifluoroborane ( 2 ) show two chemical shifts at low temperatures, due to hindered rotation about the boron–carbon bonds. The rates of rotation were determined at higher temperatures, and the corresponding free-energy barriers at coalescence were found to be 4.85±0.1 and 4.56±0.1 kcal/mol , respectively. The two barriers indicate that the cyclopropyl and vinyl groups are comparable in electron donating ability. Calculated lineshapes suggest that determination of the rotational barrier in phenyldifluoroborane by making use of the difference in coupling constants for an ortho carbon and the two fluorines may not be possible.

Cyclopentadecanone 2,4-dinitrophenylhydrazone

In the title compound, C(21)H(32)N(4)O(4), no disorder is present in the 15-membered hydrocarbon ring, which exists in an unsymmetrical quinquangular [12345] conformation. The 2,4-dinitrophenylhydrazone group is approximately perpendicular to the C(15) ring, with a dihedral angle of 84.66 (1) degrees between their best planes.

Cyclodecyl 4-nitrophenylacetate

Cyclodecyl 4-nitrophenylacetate, C18H25NO4, has its ten-membered ring in the expected diamond-lattice boat-chair-boat [2323] conformation, with the substituent 4-nitrophenylacetoxy group in the BCB IIIe position. The ester unit has the expected Z conformation, with an O=C-O-C torsion angle of -0.3 (3) degrees, and the connection to the benzene ring is nearly perpendicular to the ester, with an O=C-C-C torsion angle of 85.5 (2) degrees. An intermolecular contact exists between the ester C atom and a nitro O atom, having a C...O distance of 2.909 (2) A.