Distribution coefficient of benzoic acid in benzene and water pdf

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distribution coefficient of benzoic acid in benzene and water pdf

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Partition co-efficient of benzoic acid in benzene and water - Labmonk.pdf

E-mail: ian. The results show that all reaction pathways involved the formation of pre-reactive complexes which in turn alter reaction energy barriers. The energy barrier analysis reveals that the ortho adducts were also less vulnerable to subsequent reaction. In addition, the rate constants for the addition reactions were highest for benzoate in the aqueous phase, followed by benzoic acid in the aqueous phase, then by benzoic acid in the gas phase, consistent with electrostatic potential analysis.

However, the rate constants of hydrogen abstraction in the aqueous phase were much lower than that in the gas phase and thus, gas phase reactions are preferred. The incorporation of one explicit water molecule, for addition reactions between benzoic acid and hydroxyl radicals, lowered reaction rates in the aqueous phase by increasing the bond length between the oxygen and reacting carbon in the benzene ring. Ultrasound is effective for breaking down organic compounds in water.

Moreover, BA could also react with hydroxyl radicals inside the bubble under ultrasound irradiation. Quantum chemical reaction computation using density functional theory is a powerful tool to understand mechanisms.

These methods enable the calculation of optimized geometries for reactants and products, assessment of intermediate and transition states, and estimation of reaction kinetics for different reaction pathways with reasonable accuracy. The distribution of the intermediates is crucial to the detoxification of BA. Existing studies do not consider the difference between ortho and meta carbons on the side of carboxyl group and opposite the carboxyl group. In addition, these studies did not consider pre-reactive complexes, which can alter the kinetics of OH reactions dramatically.

Furthermore, there are few theoretical studies that compare rate constants differences between BA and BZ in the aqueous phase.

The objective of this paper is to employ density functional theory to study the transition states of six different pathways of BA with hydroxyl radicals both in gas and aqueous phases, BZ with hydroxyl radicals in the aqueous phase, and estimate the energy barrier and reaction rate constants to determine the possible distribution of intermediates including the potential effect of pre-reactive complexes.

Moreover, the influence of an individual explicit water molecule on rate constants was investigated. The optimization of adducts in the gas and aqueous phases are depicted in Fig.

In the process of hydrogen abstraction reactions, the O—H bond broke and hydrogen was abstracted to hydroxyl radicals to form a new O—H bond, leading to the formation of a water molecule. On the other hand, it was deduced that the length of the newly formed carbon—oxygen bond was below 1. In addition, the bond length of BZ products was longer than that of BA products. The transition states in the gas and liquid phases are shown in Fig. They were confirmed by a single imaginary frequency as well as the IRC analysis.

There were remarkable changes between the structures of pre-reactive complexes and transition states. The main structural changes were located around the reacting carbon and oxygen. The same trends were also found in other hydroxyl radical addition reactions both in the gas and aqueous phases. In other words, when the hydroxyl radicals reacted with a particular carbon in the benzene ring, the bond length of the reacting carbon with adjacent carbons increased as well as the length of the bonds between the carbon opposite the reacting carbon on the aromatic ring with its neighboring carbons.

The remaining two carbon—carbon bonds in the aromatic rings were shortened. This is explained by the electron density transfer of the aromatic ring. Comparing the transition states of hydroxyl radical addition to BA in gas phase versus aqueous phase, it is obvious that the transition states of the distances of oxygen and reacting carbon in the aqueous phase was longer than that in the gas phase, which could possibly be due to the formation of hydrogen bonds between BA and water, therefore, hindering the approach of hydroxyl radicals to benzene rings.

However, it is worth noting that the bond length of oxygen and the reacting carbon for BZ o -add was shorter than BA o -add, and the difference was caused by the larger steric effects of the carboxylic group than the carboxylic anion. As for the hydrogen abstraction reaction, the bond between O14 and H15 was broken, and H15 was attracted to hydroxyl radicals, generating water and a benzoic acid free radical as products.

The relative energy for the reaction between BA and hydroxyl radicals in the aqueous phase is displayed in Fig. The reaction energy barriers for the reaction from pre-reactive complexes to transition states in the aqueous medium was highest for H-abs. In addition, the energy barrier for H-abs in the aqueous phase was much higher than in the gas phase, which was possibly caused by hydrogen bonding formation between the carboxylic group and water molecules.

Therefore, the reaction in the gas phase was preferable for H-abs reaction compared to the aqueous phase reaction. According to the energy, o 2-add products were most stable among the six different reaction pathways, making them less vulnerable to subsequent reaction. As for the reaction energy between BZ and hydroxyl radicals, displayed in Fig.

This is explained because the p -add transition state was the earliest transition state among the addition reaction pathways from pre-reactive complexes for the reaction between BZ and hydroxyl radicals. The reaction rate constants in the gas and aqueous phases are listed in Table 1.

As shown, the reaction rate constants of m -add, m 2-add, p -add were higher than o -add and o 2-add for the reaction between BA and hydroxyl radicals both in the gas and aqueous phases.

There are three possible reasons to explain the phenomena, one is that the carboxyl group is an electron withdrawing group and it would decrease the electron density on the benzene ring through a resonance withdrawing effect at the ortho and para positions. Another reason is the steric influence at the ortho positions of the carboxyl group that impedes the approach of hydroxyl radicals.

The formation of hydrogen bonds between hydroxyl radicals and hydrogen in the carboxyl group is another possible factor that would inhibit the ortho position reaction. The reason why the rate constant for H-abs was highest is that benzene ring is capable of withdrawing electron density from carboxyl group by induction, making the hydrogen on the carboxyl group more active and reacting with hydroxyl group to form water.

Furthermore, the tunneling factors of H-abs were much higher than all the addition reaction pathways both in the gas and aqueous phases. Except for H-abs, the rate constants of the other five reaction pathways in the aqueous phase were much higher than in the gas phase. Furthermore, the hydrogen abstraction rates of benzoic acid were much higher than for phenol 1. The overall rate constant of the six reaction pathways computed at K, 1 atm in the aqueous medium was 1.

Assuming an uncertainty of 0. The rate constant for the reaction between BZ and hydroxyl radicals was approximately 4. Therefore, the alkaline pH is more favorable for the degradation of BA in waste water.

It is worth noting that BZ in the aqueous phase had the biggest negative electrostatic potential, followed by BA in the aqueous phase, then by BA in the gas phase, consistent with the rate constants results. Hydroxyl radicals have strong electrophilic character and tend to react at negative regions, therefore, the electrostatic potential analysis results can help explain the lower energy barrier and higher rate constants for addition reactions in the aqueous phase than in the gas phase, further confirming the accuracy of the rate constants results.

Compared with rate constants obtained by MX method, it was deduced that the rate constants predicted by CCSD T method has obvious deviation from the experimental data. Therefore, the rates constants in this study were calculated by using the MX method. The transition states with the addition of one explicit water molecule for BA and BZ are depicted in Fig.

It was deduced that the carbon—carbon length in the benzene ring of the transition states was essentially the same compared to the cases without one water molecule for both BA and BZ. The main difference was found in the variation in bond length between oxygen and the reacting carbon in benzene ring. Compared to the case without the explicit water molecule, bond lengths of the reacting carbons and oxygens were elongated for all the addition reactions between BA and hydroxyl radicals.

On the other hand, they were longer for o -add and o 2-add, and shorter for m -add, m 2-add, and p -add for the addition reactions between BZ and hydroxyl radicals. As for the rate constants, listed in Table 2 , they were different from the case without a water molecule, which was possibly caused by electron redistribution on the benzene ring.

Furthermore, the rate constants of H-abs was much smaller than for addition reaction. Therefore, the formation of hydrogen bonds between the carboxylic group and water molecules negatively influenced the rate constant for H-abs, and reaction medium should choose the gas phase or inside the bubble for the H-abs pathway. In addition, it should be noted that the joint use of implicit solvation model and one explicit water molecule may not accurately reproduce the boundary conditions between the solute and bulk, and it also requires the evaluation of entropic effects with the explicit water molecule.

Received 15th May , Accepted 12th July See DOI:

Partition co-efficient of benzoic acid in benzene and water

Solubility of dibenzothiophene in nine organic solvents: Experimental measurement and thermodynamic modelling. Approximately , tons of benzoic acid is synthesized synthetically each year for use in a large variety of industries. Benzoic acid is not soluble in water, despite the fact that it often dissolves in bases such as oil, grease and other organic compounds. An acid base extraction is a particularly popular exercise in educational chemistry because it allows students to separate a mixture of organic compounds and characterize them from their melting points afterwards. It often suffers from mistaken identity with the name of. Why is benzoic acid well soluble in benzene and other unpolar solvents, see e.

Distribution studies of Benzoic acid were done by taking solvents like Benzene, toluene, xylene, n-hexane, cyclohexane, chloroform, carbon tertrachloride, isobutyl alcohol and isoamyl alcohol. For this dm3 benzoic acid in aqueous phase was distributed in these solvents and concentration of benzoic acid was found out by titration against 0. This distribution ratio was calculated and the effect of several physical parameters on distribution of Benzoic acid was analysed. Liquid-liquid extraction is process of participationing based on the selective distribution of substance in two immiscible phases [ 1 ]. The solvent extraction minimizes the interference from the complex mixture and applicable inwide range due to requierement of sipmle appratus i. This process of separation requires just several minutes [ 2 ].

The partition coefficient of benzoic acid in benzene-water system was found to be and in buffer solutions of pH , pH and pH were , and respectively. It is expressed as the number of milliliters of solvents in which one gram of solute will dissolve.

K value of partition coefficient of benzoic acid in benzene and water

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We investigated formation of benzene an important human carcinogen from e-cigarette fluids containing propylene glycol PG , glycerol GL , benzoic acid, the flavor chemical benzaldehyde, and nicotine. In the two tank systems benzene was found to form from propylene glycol PG and glycerol GL , and from the additives benzoic acid and benzaldehyde, especially at high power settings. For tank device 2, at 6W and 25W, the formed concentrations were ND and 1.

4.5: Extraction Theory


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