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Observation of Two Conformers of Acrylic Sulfuric Anhydride by Microwave Spectroscopy
The Journal of Physical Chemistry A ( IF 2.9 ) Pub Date : 2017-11-15 00:00:00 , DOI: 10.1021/acs.jpca.7b09833
C. J. Smith 1 , Anna K. Huff 1 , Rebecca B. Mackenzie 1 , Kenneth R. Leopold 1
Affiliation  

The rotational spectrum of acrylic sulfuric anhydride (CH2═CHCOOSO2OH, AcrSA) has been observed using pulsed-nozzle Fourier transform microwave spectroscopy. The species was produced from the reaction between acrylic acid and sulfur trioxide in a supersonic jet. Spectroscopic constants are reported for both the s-cis- and s-trans-AcrSA conformers of the parent and monodeuterated (OD) isotopologues. Geometries were optimized for both conformers using M06-2X/6-311++G(3df,3pd) methods. Single-point energy calculations at the M06-2X geometries were calculated using the CCSD(T)/complete basis set method with double and triple extrapolation [CBS(D-T)]. Further calculations indicate that the anhydride results from a π2 + π2 + σ2 cycloaddition reaction within the acrylic acid–SO3 complex. Because the C═O double bond of the acrylic acid migrates from one of the COOH oxygens to the other during the reaction, the s-cis form of acrylic acid leads to the s-trans form of the anhydride and vice versa. With zero-point energy corrections applied to the CCSD(T) energies, the s-cis and s-trans forms of CH2═CHCOOSO2OH are 19.0 and 18.8 kcal/mol lower in energy than that of SO3 + their corresponding CH2═CHCOOH precursor conformation. The zero-point-corrected transition state energies for formation of the s-trans and s-cis anhydrides are 0.22 and 0.33 kcal/mol lower than those of the complexes of SO3 with s-cis and s-trans acrylic acid, respectively, indicating that the reaction is essentially barrierless. This system adds to a growing body of examples demonstrating that carboxylic acids readily add to SO3 in the gas phase to produce the corresponding carboxylic sulfuric anhydride.

中文翻译:

微波光谱法观察丙烯酸亚砜的两种共形物

丙烯酸硫酸酐的旋转光谱(CH 2 = CHCOOSO 2 OH,AcrSA)已使用脉冲喷嘴傅里叶变换微波光谱法进行了观察。该物质是由丙烯酸和三氧化硫在超音速射流中的反应产生的。光谱常数报道了两个小号--和S ^ -反式-AcrSA构象的亲本和单氘(OD)同位素异构体。使用M06-2X / 6-311 ++ G(3df,3pd)方法针对两个构象体优化了几何形状。使用CCSD(T)/具有双和三重外推法[CBS(DT)]的完全基集方法,计算了M06-2X几何形状的单点能量。进一步的计算表明,从π酸酐结果222环加成中的丙烯酸- SO反应3复合物。由于丙烯酸的C═O双键在反应过程中从一个COOH氧迁移到另一个氧,丙烯酸的s-顺式形式导致s-反式酸酐的形式,反之亦然。与零点能校正施加到CCSD(T)的能量,所述s-顺s-反CH形式2 ═CHCOOSO 2 OH是19.0和18.8千卡/摩尔降低能量比的SO 3 +它们相应的CH 2 ═CHCOOH前体的构象。形成s-反式s-顺式酸酐的零点校正过渡态能比SO 3s-顺式s-反式的配合物低0.22和0.33 kcal / mol 分别代表丙烯酸,表明该反应基本上是无障碍的。该系统增加了越来越多的实施例,表明羧酸易于在气相中添加至SO 3中以产生相应的羧酸硫酸酐。
更新日期:2017-11-16
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