The atmospheric chemistry of 2,2,5,5-tetramethyloxolane (TMO), a promising “green” solvent replacement for toluene, was investigated in laboratory-based experiments and computational calculations. Results from both absolute and relative rate studies demonstrated that the reaction OH + TMO (Reaction R1) proceeds with a rate coefficient k₁(296 K) = (3.1±0.4) $\times {\mathrm{10}}^{-\mathrm{12}}$ cm³ molecule⁻¹ s⁻¹, a factor of 3 smaller than predicted by recent structure–activity relationships. Quantum chemical calculations (CBS-QB3 and G4) demonstrated that the reaction pathway via the lowest-energy transition state was characterised by a hydrogen-bonded pre-reaction complex, leading to thermodynamically less favoured products. Steric hindrance from the four methyl substituents in TMO prevents formation of such H-bonded complexes on the pathways to thermodynamically favoured products, a likely explanation for the anomalous slow rate of Reaction (R1). Further evidence for a complex mechanism was provided by k₁(294–502 K), characterised by a local minimum at around T=340 K. An estimated atmospheric lifetime of τ₁≈3 d was calculated for TMO, approximately 50 % longer than toluene, indicating that any air pollution impacts from TMO emission would be less localised. An estimated photochemical ozone creation potential (POCP_E) of 18 was calculated for TMO in north-western Europe conditions, less than half the equivalent value for toluene. Relative rate experiments were used to determine a rate coefficient of k₂(296 K) = (1.2±0.1) $\times {\mathrm{10}}^{-\mathrm{10}}$ cm³ molecule⁻¹ s⁻¹ for Cl + TMO (Reaction R2); together with Reaction (R1), which is slow, this may indicate an additional contribution to TMO removal in regions impacted by high levels of atmospheric chlorine. All results from this work indicate that TMO is a less problematic volatile organic compound (VOC) than toluene.

中文翻译：

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通过与 OH 和 Cl 自由基的气相反应，新型“绿色”溶剂 2,2,5,5-四甲基氧戊环的大气分解化学

2,2,5,5-四甲基氧戊环 (TMO) 是一种很有前途的甲苯“绿色”溶剂替代品，其大气化学在基于实验室的实验和计算中得到了研究。绝对和相对速率研究的结果表明，反应 OH  +  TMO（反应 R1）以速率系数k ₁ (296 K)  =  ( 3.1±0.4 ) 进行$\times {\mathrm{10}}^{-\mathrm{12}}$ cm ³  molecule ⁻¹  s ⁻¹，比最近的构效关系预测的小 3 倍。量子化学计算（CBS-QB3 和 G4）表明，通过最低能量过渡态的反应途径以氢键预反应络合物为特征，导致热力学上不太受欢迎的产物。TMO 中四个甲基取代基的空间位阻阻止了在通往热力学有利产品的途径上形成此类氢键络合物，这可能是反应 (R1) 异常缓慢的原因。k ₁ (294–502 K)提供了复杂机制的进一步证据，其特征是在T =340附近出现局部最小值 K. 计算出 TMO 的估计大气寿命为τ ₁ ≈3  d，比甲苯长约 50%，表明 TMO 排放对空气污染的影响较小。在欧洲西北部的条件下，TMO的估计光化学臭氧产生潜力 (POCP _{E ) 为 18，不到甲苯等效值的一半。}相对速率实验用于确定速率系数k ₂ (296 K)  =  ( 1.2±0.1 ) $\times {\mathrm{10}}^{-\mathrm{10}}$ cm ³ 分子^-1  s ^-1 对于 Cl  +  TMO（反应 R2）；与缓慢的反应 (R1) 一起，这可能表明在受高浓度大气氯影响的地区对 TMO 的去除有额外贡献。这项工作的所有结果表明，与甲苯相比，TMO 是一种问题较少的挥发性有机化合物 (VOC)。