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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Quantitative Scale for the Extent of Conjugation of Carbonyl Groups: 'Carbonylicity' Percentage as a Chemical Driving Force
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Quantitative Scale for the Extent of Conjugation of Carbonyl Groups: 'Carbonylicity' Percentage as a Chemical Driving Force

机译：羰基共轭程度的定量尺度：“碳基”百分比作为化学驱动力

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摘要

Despite the carbonyl group being one of the most pervasive chemical building blocks in natural, synthetic, and industrial processes, its exact description in terms of precise quantification of the degree of carbonyl conjugation has yet to be determined. The present work suggests a novel yet simple method for quantifying the conjugation in general carbonyl groups (such as ketones, aldehydes, carboxylic acids and their respective halogenides, amides, etc.) on a linear scale, defined as the "carbonylicity scale". This was achieved by use of the computed enthalpy of hydrogenation (ΔH_(H2)) of the >C=O group in the compounds examined. In the present conceptual work, the ΔH_(H2) value for formate ion is used to define complete conjugated character (carbonylicity = +100%), while formaldehyde represents complete absence of conjugation (carbonylicity = 0%). The component ΔH_(H2) values were computed at differing levels of theory, providing a nearly "method-independent" measure of carbonylicity computationally. A total of 49 common carbonyl compounds were used as accuracy scoring criteria of the methodology. For the compounds examined, correlations have been made between the computed carbonylicity percentage and the >C=O proton affinities, IR frequencies, and their reactivity values in a nucleophilic addition reaction. Selected chemical reactions were also studied to illustrate the utility of carbonylicity scale. Examples herein include demonstrating that change in the carbonylicity value represents a thermodynamic driving force in acylation reactions. The definition was extended to substituted thiocarbonyl and imino compounds.
机译：尽管羰基是天然，合成和工业过程中最普遍的化学结构单元之一，但仍需确定其在羰基结合度的精确定量方面的确切描述。本工作提出了一种新颖而简单的方法，用于以线性标度（称为“羰基度标度”）量化一般羰基（如酮，醛，羧酸及其各自的卤化物，酰胺等）的共轭。这是通过使用所研究化合物中> C = O基团的计算的氢化焓（ΔH_（H2））实现的。在本概念性工作中，甲酸根离子的ΔH_（H2）值用于定义完全的共轭特性（羰基度= + 100％），而甲醛表示完全不存在共轭（羰基度= 0％）。组分ΔH_（H2）的值是在不同的理论水平上计算的，从而通过计算提供了几乎“与方法无关”的羰基度度量。共有49种常见的羰基化合物用作该方法的准确性评分标准。对于所检查的化合物，已计算出的羰基百分比与亲核加成反应中的> C = O质子亲和力，IR频率及其反应性值之间具有相关性。还研究了选定的化学反应以说明羰基度规模的实用性。本文的实例包括证明羰基值的变化代表酰化反应中的热力学驱动力。该定义扩展到取代的硫代羰基和亚氨基化合物。

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