Quantitative structure-property relationship (QSPR) is performed as a means to predict octane number of hydrocarbons via correlating properties to parameters calculated from molecular structure; such parameters are molecular mass , hydration energy , boiling point , octanol/water distribution coefficient , molar refractivity , critical pressure , critical volume , and critical temperature . Principal component analysis (PCA) and multiple linear regression technique (MLR) were performed to examine the relationship between multiple variables of the above parameters and the octane number of hydrocarbons. The results of PCA explain the interrelationships between octane number and different variables. Correlation coefficients were calculated using M.S. Excel to examine the relationship between multiple variables of the above parameters and the octane number of hydrocarbons. The data set was split into training of 40 hydrocarbons and validation set of 25 hydrocarbons. The linear relationship between the selected descriptors and the octane number has coefficient of determination , statistical significance , and standard errors . The obtained QSPR model was applied on the validation set of octane number for hydrocarbons giving and . 1. Introduction Octane rating or octane number is a standard measure of the performance of gasoline fuel. The most common type of octane rating worldwide is the research octane number (RON) and motor octane number (MON). Octanes are a family of hydrocarbon that are typical components of gasoline. The octane rating of gasoline is measured in a test engine and is defined by comparison with the mixture of 2,2,4-trimethylpentane (isooctane) and heptane that would have the same antiknocking capacity as the gasoline fuel under test. For example, gasoline with the same knocking characteristics as a mixture of 90% isooctane and 10% heptane would have an octane rating of 90. The ASTM standard for reporting this measurement is an internal combustion engine in which octane is measured by interpolating between the nearest standards above and below the unknown sample [1]. The procedure is time consuming, involves expensive and maintenance intensive equipment, and requires skilled labour. A more thorough understanding of the relations between the structure of alkanes and their physicochemical properties and the empirical rules of octane number (ON) dependence on the structure of alkanes are discussed by A. Perdih and F. Perdih [2]. The relation between the structure of hydrocarbons and their octane was studied using a number of topological
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