Quantitative Structure−Odor Relationships of Aliphatic Esters Using Topological Indices

Abstract

Quantitative structure-activity relationships (QSAR) were used in this study to relate the structural parameters (electronic, topological, etc.) to the odor of 27 aliphatic esters previously evaluated by Rossiter. Rossiter used the Hansch approach, principal component analysis and comparative molecular field analysis (CoMFA) to predict the odor of these esters. Different structural parameters were selected, such as topological, physicochemical, and quantum-chemical indices, to find an equation to predict the molecular factors that determine the fruit odor of these compounds and to compare such results with those obtained by Rossiter. Two significant correlation equations were obtained with the following molecular descriptors: one with the electrotopological-state index related to the carbon atom of the carbonyl group (S(C)(=)(O)), the Kappa index ((2)Kappa), and the topological-state index related to the oxygen on the alcoholic side of the molecule (T(-)(O)(-)), and the other with (2)Kappa, S(C)(=)(O), and the energy of the highest occupied molecular orbital (E(HOMO)). The model found had a good predictive ability as established by cross-validation r(2)(cv) values and thus can be used to help in the prediction of odor of similar compounds. This method is simplier than the methods used by Rossiter and represents a reliable QSAR alternative in predicting the fruit odor of such aliphatic esters.

Comparison of Volatile Profiles of Meads and Related Unifloral Honeys: Traceability Markers

“…A particularly high difference in ester percentage between the not boiled and the boiled honeys was related to the content of ethyl decanoate and ethyl dodecanoate in the not boiled (up to 23.91% and 13.43%, respectively) and in the boiled (up to 4.26% and 4.84%, respectively). Aliphatic esters are responsible for fruity odors [ 14 ]. Ethyl decanoate and ethyl dodecanoate are described, respectively, as sweet, fatty, nut-like, with a winey-cognac odor and oily, fatty, floral, with fatty fruity taste [ 13 , 15 ].…”

Quantitative Structure−Activity (Affinity) Relationship (QSAR) Study on Protonation and Cationization of α-Amino Acids

“…[42][43][44] The KA value is large for linear structures but small for branching structures. 44 In general, the flexibility of a molecule is directly related to the degree of linearity. 45 All AA have a common backbone structure; thus, the variation in KA is mainly attributed to the linear flexible side chain, such as Arg, whose KA value is largest.…”

“…As a consequence of this definition, KA indicates the degree of linearity of bonding patterns for a molecule. − The KA value is large for linear structures but small for branching structures . In general, the flexibility of a molecule is directly related to the degree of linearity .…”

Stationary Phases for Complexation Gas Chromatography and Microextraction Methods

“…Research into the prediction of retention indices of branched alkenes using a semi‐empirical chemometric method on several stationary phases of low polarity has been successfully carried out by Junkes et al . Their work has shown a high efficiency of the semi‐empirical topological index in the construction of models describing the retention of linear unsaturated olefins.…”