{"title":"从B / 2A′(3p)←X / 2A′”电子谱和从头计算得出的羟基甲基(CH2OH)自由基和阳离子的结构和热化学性质","authors":"Russell D. Johnson, Jeffrey W. Hudgens","doi":"10.1021/jp961399+","DOIUrl":null,"url":null,"abstract":"<p >B? <sup>2</sup>A‘(3p) ← X? <sup>2</sup>A‘‘ spectra of the isotopically substituted hydroxymethyl radicals (CH<sub>2</sub>OH, CH<sub>2</sub>OD, CD<sub>2</sub>OH, CD<sub>2</sub>OD) were observed between 39?700 and 43?000 cm<sup>-1</sup> by 2+1, 2+2, and 1+1 resonance-enhanced multiphoton ionization (REMPI) spectroscopy. Analyses of the vibrational hot bands in these spectra show that the ν<sub>8</sub> torsion modes and ν<sub>9</sub> CH<sub>2</sub>-wag mode are strongly coupled and governed by nonharmonic potential energy functions; for example, for <sup>12</sup>CH<sub>2</sub><sup>16</sup>OH(X? <sup>2</sup>A‘‘) we obtain 2ν<sub>8</sub> = 846 ± 6 cm<sup>-1</sup>(1σ), 1ν<sub>9</sub> = 234 ± 5 cm<sup>-1</sup>, and 2ν<sub>9</sub> = 615 ± 6 cm<sup>-1</sup>. Using MP2/6-311G(2df,2p) <i>ab initio</i> calculations, we constructed the two-dimensional potential energy surfaces that govern the ν<sub>8</sub> torsion modes and ν<sub>9</sub> CH<sub>2</sub>-wag in the X? <sup>2</sup>A‘‘ radical and the X? <sup>1</sup>A‘ cation core of the B? <sup>2</sup>A‘(3p) Rydberg state. Energy levels calculated with these potential energy surfaces account for the REMPI bands originating from the ν<sub>8</sub> hindered rotor and the ν<sub>9</sub> CH<sub>2</sub>-wag modes. The experimental and <i>ab initio</i> results lead to improved heat capacities and entropies (<i>S</i>°<sub>298.15</sub>(CH<sub>2</sub>OH) = 244.170 ± 0.018 J (mol K)<sup>-1</sup>). <i>Ab initio</i> CBS-QCI/APNO calculations predict that Δ<sub>f</sub><i>H</i>°<sub>298.15</sub>(CH<sub>2</sub>OH) = ?18.4 ± 1.3 kJ mol<sup>-1</sup>. Re-evaluation of photoionization data yields IP<sub>a</sub>(CH<sub>2</sub>OH) = 7.562 ± 0.004 eV. Re-evaluated photoionization appearance data, kinetic equilibrium data, and shock tube data indicate that Δ<sub>f</sub><i>H</i>°<sub>0</sub>(CH<sub>2</sub>OH<sup>+</sup>) = 718.1 ± 1.8 kJ mol<sup>-1</sup>, Δ<sub>f</sub><i>H</i>°<sub>298.15</sub>(CH<sub>2</sub>OH<sup>+</sup>) = 716.4 ± 1.8 kJ mol<sup>-1</sup>, Δ<sub>f</sub><i>H</i>°<sub>0</sub>(CH<sub>2</sub>OH) = ?11.5 ± 1.3 kJ mol<sup>-1</sup>, and Δ<sub>f</sub><i>H</i>°<sub>298.15</sub>(CH<sub>2</sub>OH) = ?17.8 ± 1.3 kJ mol<sup>-1</sup>. We report the proton affinity, PA<sub>0</sub>(CH<sub>2</sub>O) = 705.2 ± 1.9 kJ mol<sup>-1</sup>. Thermochemical tables based upon these values are presented for CH<sub>2</sub>OH and CH<sub>2</sub>OH<sup>+</sup>. </p>","PeriodicalId":58,"journal":{"name":"The Journal of Physical Chemistry ","volume":null,"pages":null},"PeriodicalIF":2.7810,"publicationDate":"1996-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1021/jp961399+","citationCount":"69","resultStr":"{\"title\":\"Structural and Thermochemical Properties of Hydroxymethyl (CH2OH) Radicals and Cations Derived from Observations of B̃ 2A‘(3p) ← X̃ 2A‘‘ Electronic Spectra and from ab Initio Calculations\",\"authors\":\"Russell D. Johnson, Jeffrey W. Hudgens\",\"doi\":\"10.1021/jp961399+\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p >B? <sup>2</sup>A‘(3p) ← X? <sup>2</sup>A‘‘ spectra of the isotopically substituted hydroxymethyl radicals (CH<sub>2</sub>OH, CH<sub>2</sub>OD, CD<sub>2</sub>OH, CD<sub>2</sub>OD) were observed between 39?700 and 43?000 cm<sup>-1</sup> by 2+1, 2+2, and 1+1 resonance-enhanced multiphoton ionization (REMPI) spectroscopy. Analyses of the vibrational hot bands in these spectra show that the ν<sub>8</sub> torsion modes and ν<sub>9</sub> CH<sub>2</sub>-wag mode are strongly coupled and governed by nonharmonic potential energy functions; for example, for <sup>12</sup>CH<sub>2</sub><sup>16</sup>OH(X? <sup>2</sup>A‘‘) we obtain 2ν<sub>8</sub> = 846 ± 6 cm<sup>-1</sup>(1σ), 1ν<sub>9</sub> = 234 ± 5 cm<sup>-1</sup>, and 2ν<sub>9</sub> = 615 ± 6 cm<sup>-1</sup>. Using MP2/6-311G(2df,2p) <i>ab initio</i> calculations, we constructed the two-dimensional potential energy surfaces that govern the ν<sub>8</sub> torsion modes and ν<sub>9</sub> CH<sub>2</sub>-wag in the X? <sup>2</sup>A‘‘ radical and the X? <sup>1</sup>A‘ cation core of the B? <sup>2</sup>A‘(3p) Rydberg state. Energy levels calculated with these potential energy surfaces account for the REMPI bands originating from the ν<sub>8</sub> hindered rotor and the ν<sub>9</sub> CH<sub>2</sub>-wag modes. The experimental and <i>ab initio</i> results lead to improved heat capacities and entropies (<i>S</i>°<sub>298.15</sub>(CH<sub>2</sub>OH) = 244.170 ± 0.018 J (mol K)<sup>-1</sup>). <i>Ab initio</i> CBS-QCI/APNO calculations predict that Δ<sub>f</sub><i>H</i>°<sub>298.15</sub>(CH<sub>2</sub>OH) = ?18.4 ± 1.3 kJ mol<sup>-1</sup>. Re-evaluation of photoionization data yields IP<sub>a</sub>(CH<sub>2</sub>OH) = 7.562 ± 0.004 eV. Re-evaluated photoionization appearance data, kinetic equilibrium data, and shock tube data indicate that Δ<sub>f</sub><i>H</i>°<sub>0</sub>(CH<sub>2</sub>OH<sup>+</sup>) = 718.1 ± 1.8 kJ mol<sup>-1</sup>, Δ<sub>f</sub><i>H</i>°<sub>298.15</sub>(CH<sub>2</sub>OH<sup>+</sup>) = 716.4 ± 1.8 kJ mol<sup>-1</sup>, Δ<sub>f</sub><i>H</i>°<sub>0</sub>(CH<sub>2</sub>OH) = ?11.5 ± 1.3 kJ mol<sup>-1</sup>, and Δ<sub>f</sub><i>H</i>°<sub>298.15</sub>(CH<sub>2</sub>OH) = ?17.8 ± 1.3 kJ mol<sup>-1</sup>. We report the proton affinity, PA<sub>0</sub>(CH<sub>2</sub>O) = 705.2 ± 1.9 kJ mol<sup>-1</sup>. Thermochemical tables based upon these values are presented for CH<sub>2</sub>OH and CH<sub>2</sub>OH<sup>+</sup>. </p>\",\"PeriodicalId\":58,\"journal\":{\"name\":\"The Journal of Physical Chemistry \",\"volume\":null,\"pages\":null},\"PeriodicalIF\":2.7810,\"publicationDate\":\"1996-12-19\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://sci-hub-pdf.com/10.1021/jp961399+\",\"citationCount\":\"69\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"The Journal of Physical Chemistry \",\"FirstCategoryId\":\"1\",\"ListUrlMain\":\"https://pubs.acs.org/doi/10.1021/jp961399%2B\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"\",\"JCRName\":\"\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"The Journal of Physical Chemistry ","FirstCategoryId":"1","ListUrlMain":"https://pubs.acs.org/doi/10.1021/jp961399%2B","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
Structural and Thermochemical Properties of Hydroxymethyl (CH2OH) Radicals and Cations Derived from Observations of B̃ 2A‘(3p) ← X̃ 2A‘‘ Electronic Spectra and from ab Initio Calculations
B? 2A‘(3p) ← X? 2A‘‘ spectra of the isotopically substituted hydroxymethyl radicals (CH2OH, CH2OD, CD2OH, CD2OD) were observed between 39?700 and 43?000 cm-1 by 2+1, 2+2, and 1+1 resonance-enhanced multiphoton ionization (REMPI) spectroscopy. Analyses of the vibrational hot bands in these spectra show that the ν8 torsion modes and ν9 CH2-wag mode are strongly coupled and governed by nonharmonic potential energy functions; for example, for 12CH216OH(X? 2A‘‘) we obtain 2ν8 = 846 ± 6 cm-1(1σ), 1ν9 = 234 ± 5 cm-1, and 2ν9 = 615 ± 6 cm-1. Using MP2/6-311G(2df,2p) ab initio calculations, we constructed the two-dimensional potential energy surfaces that govern the ν8 torsion modes and ν9 CH2-wag in the X? 2A‘‘ radical and the X? 1A‘ cation core of the B? 2A‘(3p) Rydberg state. Energy levels calculated with these potential energy surfaces account for the REMPI bands originating from the ν8 hindered rotor and the ν9 CH2-wag modes. The experimental and ab initio results lead to improved heat capacities and entropies (S°298.15(CH2OH) = 244.170 ± 0.018 J (mol K)-1). Ab initio CBS-QCI/APNO calculations predict that ΔfH°298.15(CH2OH) = ?18.4 ± 1.3 kJ mol-1. Re-evaluation of photoionization data yields IPa(CH2OH) = 7.562 ± 0.004 eV. Re-evaluated photoionization appearance data, kinetic equilibrium data, and shock tube data indicate that ΔfH°0(CH2OH+) = 718.1 ± 1.8 kJ mol-1, ΔfH°298.15(CH2OH+) = 716.4 ± 1.8 kJ mol-1, ΔfH°0(CH2OH) = ?11.5 ± 1.3 kJ mol-1, and ΔfH°298.15(CH2OH) = ?17.8 ± 1.3 kJ mol-1. We report the proton affinity, PA0(CH2O) = 705.2 ± 1.9 kJ mol-1. Thermochemical tables based upon these values are presented for CH2OH and CH2OH+.