Enthalpies of combustion and formation of 1,1-bis(difluoroamino) heptane. N-F thermochemical bond energy

Abstract

The enthalpy of combustion of liquid 1,1 -bis(difluoroamino)heptane was measured in a rotating-bomb calorimeter. The enthalpy of vaporization was estimated. The experimental enthalpy of combustion and the estimated enthalpy of vaporization were used to calculate the following values, in kcal. per mole at 298.15°K ., for this compound: standard enthalpy of formation of the liquid from graphite and gaseous hydrogen, fluorine, and nitrogen, -64.82; standard enthalpy of formation of the gas (estimated), -52.8. The N-F thermochemical bond energy in 1,1-bis-(difluoroamino) heptane was estimated to 67.3 kcal., about the same as the N-F thermochemical bond energy in NF3, N2F4, and 1,2-bis(difluoroamino)-4-methylpentane, but several kilocalories less than the N-F thermochemical bond energy in perfluoropiperidine.

Cavitation of liquid flow in electrospray mass spectrometry especially for addition of internal calibrant in ‘accurate mass’ measurements

“…The fact that the relative stabilities of X 2 PN>XPNX with X=F are reversed compared to that with X=H, CH 3 can primarily be attributed to the significant difference in bond energies of the two bonds15 involved: PF (544 kJ mol −1 )16 >NF (278 kJ mol −1 ) 17. Both the rather high singlet–triplet energy gap (58.6 kJ mol −1 ) and the high barrier (229.3 kJ mol −1 ) for the 1,2‐fluorine shift to trans ‐FPNF are in accord with structure 2 in Equation (2).…”