- Brief introductions to the MP treatment of atoms and molecules: Levine IN (2000) Quantum
chemistry, 5th edn. Prentice Hall, Engelwood Cliffs, NJ, pp 563–568; Lowe JP (1993)
Quantum chemistry, 2nd edn. Academic Press, New York, pp 369–370; Leach AR (2001)
Molecular modelling, 2nd edn. Prentice Hall, Essex, England, pp 114–117 - Levine IN (2000) Quantum chemistry, 5th edn. Prentice Hall, Engelwood Cliffs, NJ,
Chapter 9 - Møller C, Plesset MS (1934) Phys Rev 46:618
- Binkley JS, Pople JA (1975) Int J Quant Chem 9:229
- Cramer CJ (2004) Essentials of computational chemistry, 2nd edn. Wiley, Chichester, UK,
Sections 7.4.1 and 7.4.2 - Lowe JP (1993) Quantum chemistry, 2nd edn. Academic Press, New York, pp 367–368
- Szabo A, Ostlund NS (1989) Modern quantum chemistry. McGraw-Hill, New York, p 353;
Leach AR (2001) Molecular modelling, 2nd edn. Prentice Hall, Essex, England, p 115 - Boldyrev A, Schleyer PvR, Higgins D, Thomson C, Kramarenko SS (1992) J Comput Chem
9:1066. Fluoro- and difluorodiazomethanes are minima by HF calculations, but are transition
states by the MP2 method
92.H 2 C¼CHOH reactionThe only quantitative information on the barrier for this reaction
seems to be: Saito S (1976) Chem Phys Lett 42:399, halflife in the gas phase in a Pyrex flask
at room temperature ca. 30 min. From this one calculates (Section “Kinetics; Calculating
Reaction Rates”, Eq. (5.202)) a free energy of activation of 93 kJ mol#^1. Since isomerization
may be catalyzed by the walls of the flask, the purely concerted reaction may have a much
higher barrier. This paper also shows by microwave spectroscopy that ethanol has the O–H
bondsynto the C¼C. The most reliable measurement of the ethenol/ethanal equilibrium
constant, by flash photolysis, is 5.89' 10 #^7 in water at room temperature (Chiang Y, Hojatti
M, Keeffe JR, Kresge AK, Schepp NP, Wirz J (1987) J Am Chem Soc 109:4000). This gives
a free energy of equilibrium of 36 kJ mol#^1 (ethanal 36 kJ mol#^1 below ethenol). The
accurate G3MP2 method [Section “Thermodynamics; High-Accuracy Calculations”] places
the gas phase free energy of ethanol 43 kJ mol#^1 below that of ethenol.HNC reactionThe
barrier for rearrangement of HNC to HCN has apparently never been actually measured. The
equilibrium constant in the gas phase at room temperature was calculated (Maki AG, Sams
RL (1981) J Chem Phys 75:4178) at 3.7' 10 #^8 , from actual measurements at higher
temperatures; this gives a free energy of equilibrium of 42 kJ mol#^1 (HCN 42 kJ mol#^1
below HNC). The G3MP2 method places the gas phase free energy of HCN 59 kJ mol#^1
below that of HNC.CH 3 NC reactionThe reported experimental activation energy is 161 kJ
mol#^1 (Wang D, Qian X, Peng J (1996) Chem Phys Lett 258:149; Bowman JM, Gazy B,
Bentley JA, Lee TJ, Dateo CE (1993) J Chem Phys 99:308; Rabinovitch BS, Gilderson PW
(1965) J Am Chem Soc 87:158; Schneider FW, Rabinovitch BS (1962) J Am Chem Soc
84:4215). The energy difference between CH 3 NC and CH 3 CN has apparently never been
actually measured. The G3MP2 method places the gas phase free energy of CH 3 CN 99 kJ
mol#^1 below that of CH 3 NC.Cyclopropylidene reactionNeither the barrier nor the equilib-
rium constant for the cyclopropylidene/allene reaction have been measured. The only direct
experimental information of these species come from the failure to observe cyclopropylidene
at 77 K (Chapman OL (1974) Pure Appl Chem 40:511). This and other experiments
(references in Bettinger HF, Schleyer PvR, Schreiner PR, Schaefer HF (1997) J Org Chem
62:9267 and in Bettinger HF, Schreiner PR, Schleyer PvR, Schaefer HF (1996) J Phys Chem
100:16147) show that the carbene is much higher in energy than allene and rearranges very
rapidly to the latter. Bettinger et al. (1997) (above) calculate the barrier to be 21 kJ mol#^1
(5 kcal mol#^1 ). The G3MP2 method places the gas phase free energy of allene 283 kJ mol#^1
below that of cyclopropylidene - (a) Saebø S, Pulay P (1987) J Chem Phys 86:914. (b) Pulay P (1983) Chem Phys Lett
100:151 - (a) Vahtras O, Alml€of J, Feyereisen MW, Pulay P (1993) Chem Phys Lett 213:514. (b)
Feyereisen M, Fitzgerald G, Komornicki A (1993) Chem Phys Lett 208:359. (c) The virtues
378 5 Ab initio Calculations