Spada Lorenzo, Evangelisti Luca, Li Weixing, Orlacchio Ramona, Caminati Walther
Dipartimento di Chimica , "G. Ciamician" dell'Università , Via Selmi 2 , I-40126 Bologna , Italy.
J Phys Chem A. 2019 Mar 7;123(9):1785-1789. doi: 10.1021/acs.jpca.8b11294. Epub 2019 Feb 21.
The rotational spectrum of the 1:1 complex formic acid-isopropylformate (FA-IPF) has been first observed when trying to assign the pulsed jet Fourier transform microwave (FTMW) spectrum of the adduct formic acid-2-propanol, by expanding a binary mixture of HCOOH and 2-propanol in He. The strong FTMW spectrum of isopropylformate, formed by the esterification reaction, was observed instead. However, when HCOOH was in excess in the binary mixture, it was possible to observe and assign the rotational spectrum of FA-IPF. Later on a much intense spectrum of FA-IPF was obtained, when combining FA with IPF. Finally, the spectra of five isotopologues of the most stable isomer of formic acid-isopropylformate have been observed by means of rotational spectroscopy in supersonic expansion. Some of them, HCOOH-(CH)CHOOCD and HCOOH-(CH)CDOOCH have been synthesized in the MW cavity by using DCOOH or (CH)CDOH as precursors in the esterification process. In the observed isomer of the complex, the two subunits are linked to each other by a standard O-H···O and a weak C-H···O hydrogen bond. The dissociation energy has been estimated to be 34.1 kJ·mol.
在尝试对甲酸 - 2 - 丙醇加合物的脉冲喷射傅里叶变换微波（FTMW）光谱进行归属时，通过在氦气中膨胀甲酸（HCOOH）和2 - 丙醇的二元混合物，首次观测到了1:1络合物甲酸 - 异丙基甲酸酯（FA - IPF）的转动光谱。然而，观测到的却是由酯化反应形成的异丙基甲酸酯的强FTMW光谱。不过，当二元混合物中HCOOH过量时，就有可能观测并归属FA - IPF的转动光谱。后来，将FA与IPF混合时，得到了强度更高的FA - IPF光谱。最后，通过超声速膨胀转动光谱法观测到了甲酸 - 异丙基甲酸酯最稳定异构体的五种同位素变体的光谱。其中一些，如HCOOH - (CH)CHOOCD和HCOOH - (CH)CDOOCH，是在MW腔中通过使用DCOOH或(CH)CDOH作为酯化过程的前体合成的。在观测到的络合物异构体中，两个亚基通过一个标准的O - H···O氢键和一个弱的C - H···O氢键相互连接。其离解能估计为34.1 kJ·mol。
