| Abstract
| - Structures and thermochemical properties,,and Cp(T) of three (mono-, di-, and tri-) chloromethanols; three chloromethoxy and the two hydroxychloromethyl radicals are determined by ab initio anddensity functional calculations. The molecular structures and vibration frequencies are determined at the B3LYP/6-31G(d,p) density functional level, with single point calculations for the energy at the B3LYP/6-311+G(3df,2p), QCISD(T)/6-31G(d,p), and CBSQ//B3LYP/6-31G(d,p) levels. The vibration frequencies are scaledfor zero-point energies and for thermal corrections. The enthalpies of formation () are determined ateach calculation level using several isodesmic reactions. Standard entropy () and heat capacity (Cp(T)'s,300 ≤ T/K ≤ 1500) from vibrational, translational, and external rotational contributions are calculated usingthe rigid-rotor-harmonic-oscillator approximation based on the vibration frequencies and structures obtainedfrom the density functional study. Potential barriers for internal rotation of the hydroxyl group are calculatedat the B3LYP/6-31G(d,p) level, and hindered internal rotational contributions to entropy and heat capacityare calculated by summation over the energy levels obtained by direct diagonalization on the Hamiltonianmatrix of hindered internal rotations. An evaluation of data from the isodesmic reactions at each calculationlevel results in the enthalpy of formation values: −58.07 ± 0.69, −65.88 ± 0.76, and −65.96 ± 0.76 kcal/mol for mono-, di-, and trichloromethanol, respectively. The standard enthalpies for the mono-, di-, andtrichloromethoxy radicals are −5.13 ± 2.18, −7.65 ± 2.25, and −9.05 ± 2.24 kcal/mol, respectively. Thestandard enthalpies for the hydroxymono- and hydroxydichloromethyl radicals are −14.46 ± 1.75 and −22.54± 1.83 kcal/mol. Bond energies for the RO−H bond are 105.04, 110.33, and 109.01 kcal/mol, respectively.Bond energies for the R−OH bonds are 95.20, 98.81, and 94.39 kcal/mol, respectively. Groups for use inBenson type additivity estimations are determined for the carbon bonded to oxygen and chlorine(s). Theenthalpy values for the C/Cl/H2/O, C/Cl2/H/O, and C/Cl3/O groups are −20.17, −27.98, and −28.06 kcal/mol, respectively. Hydrogen bond increment groups for the chloromethoxy and hydroxychloromethyl radicalsare also developed. The bond energies andvalues suggest that the electronegative Cl(s) on the methylserve to increase and RO−H bond energy.for C•H2OH, CH3C•HOH, and C2H5O• are also determinedand compared with literature data, and recommended values are −3.97 ± 0.22, −13.34 ± 0.84, and −3.90± 1.27 kcal/mol, respectively.
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