According to the previous study by Jhamb, Liang, Gani et al., (2018), the group contribution method in the field of chemistry is usually known to be making estimations and predictions of thermodynamics and other molecular structure properties. It is said to be an extension of the Lydersen method as they have similarities in the group, some parameters, and formula. The Joback’s approach, therefore, utilizes predictions of eleven pure thermodynamic components which are commonly used and are of great importance only from the molecular structure. It uses basic structures of the chemical molecules in the calculation of thermos-physical properties as summed parameters. The method uses the principle that there is insignificant interaction between the functional groups; hence additive contributions are used.
Physical Properties of N-Pentanol
N-Pentanol is also known as 1-pentanol or pentan-1-ol and is a type of alkyl alcohol containing 5 atoms of carbon. The molecular formula of n-Pentanol is presented as C5H11OH, and it is in a liquid state at room temperature. It is colorless and emits a characteristic unpleasant odor. This range from mild to very strong depending on the prevailing conditions, which make it a bit toxic when ingested. Pentanol is less dense as compared to water density and have a Flashpoint of 910 F. It has a boiling point of 2800F, and when in a gaseous state, the vapour is denser than air. The experimental data in other literature shows that the pentanol isomers are very important as they can be used as biofuels. This is because they significantly have higher molar enthalpies which enable them to be used as fuels.
Drawbacks of Joback’s Group Contribution Method
In as much as the Joback’s method have got advantages including a simple group scheme which is easy to assign, it also has few limitations just like any other research experiments.
According to Tula, Eden & Gani (2015), the new research was done on the same matter, Joback’s method has been found to have some limitations whereby the technique is considered more accurate than the other methods while the high accuracy is not guaranteed. The common molecules are not sufficiently covered in Joback’s method, for instance, the aromatic compounds have not been well distinguished from the normal ring. The lack of distinction between the two causes a severe mistake since there is a substantial difference between the aromatic compounds and aliphatic compounds. The limitations come as a result of the limited database used by Joback and Reid in their experiment, which was only able to cover a small number of molecules. The current studies have used data banks such as Dortmund data bank to avoid such problems in their experiments.
In the Joback’s method, the problem also arises from the formula used in the standard boiling point prediction whereby a constant contribution of the additional groups was assumed in a homogenous series just like in the case of alkanes. In this formula, the real behaviour of the standard boiling points is not described correctly. The method is only accurate in estimating the middle-sized components, while in small and large segments, the higher deviations are shown. The expected output should be a decrease in the contributions as the number of group increases as opposed to the regular contribution, (Baghban, Kardani &Habibzadeh, 2017). These make the significant problems of Joback and Reid’s research as it remain one of the fundamental techniques to be considered in the molecular properties of alcohols.
Baghban, A., Kardani, M. N., & Habibzadeh, S. (2017). Prediction viscosity of ionic liquids using a hybrid LSSVM and group contribution method. Journal of Molecular Liquids, 236, (2017): 452-464.
Jhamb, S., Liang, X., Gani, R., & Hukkerikar, A.S. (2018). Estimation of physical properties of amino acids by the group-contribution method. Chemical Engineering Science, 175, 148-161.
Tula, A.K., Eden, M. R., & Gani, R. (2015). Process synthesis, design, and analysis using a process-group contribution method. Computers and Chemical Engineers, 81, 245-259.