Enthalpy, entropy and heat capacity property estimation for cyclic molecules using Benson's group additivity method require the use of ring correction terms. Ring correction terms are estimated from the thermodynamic properties of the cyclic molecule being considered. In the absence of literature values a procedure is proposed to predict these thermodynamic values.
Benson's Group additivity method does not fully account for the interactions between bulky group or atom substituents on the aromatic ring. In order to have accurate thermodynamic properties for these compounds, a data base is generated with ortho, meta and Para interactions for (Cl-Cl), (Cl-OH), (OH-OH), (CH3-CH3), (CH3- OH) and (F-F) to be used with Benson's group method. In case of three or more methyls, buttress effect to be used has been included. In case of multiply substituted aromatics a counting scheme is proposed to obtain effective number of interactions.
The ring correction groups and group interactions are used with Benson' group method to predict thermodynamic properties of likely candidate precursors to dioxin formation during the oxidation/incineration of chloroaromatics. Based on these thermodynamic properties a set of reaction pathways is proposed which could lead to the formation of dioxins. A comparison is carried out between reaction systems with chlorine substituents with similar systems without chlorines to explain larger formation of chlorinated dioxins. Quantum Rice-Ramsperger-Kassel calculations for determining kinetic (rate constants) are carried out for select pathways.
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