Infrared and Raman Spectra of Substituted Hydrazines. I. Methylhydrazine

The infrared gas phase spectra of methylhydrazine (NH₂NHCH₃), methylhydrazine‐d₃ (ND₂NDCH₃), and methylhydrazine‐d₆(ND₂NDCD₃), have been measured from 33 to 4000 cm⁻¹. The infrared and Raman spectra of the corresponding compounds in the liquid state have also been recorded. A complete vibrational analysis based on band intensity, position, and isotopic shift is presented. A series of sharp $Q$ branches in the far‐infrared region facilitated calculations of the torsional barriers. By assuming that a symmetrical threefold cosine potential governs both rotors in NH₂NHCH₃ we calculate barriers of 3.67 and 3.72 kcal/mole for the methyl and amino torsions, respectively. The intensity of the 3182‐cm⁻¹ line of NH₂NHCH₃ has been studied as a function of temperature. The $\mathrm{\Delta H°}$ for H‐bond formation is found to be − 418 cal/mole. Thermodynamic functions for NH₂NHCH₃ have been calculated for the temperature range 200°–3000°K on the basis of a rigid rotator, harmonic oscillator model.