The Joback boiling point method is a group contribution technique applicable to a broad range of organic chemicals. The technique is very easy to use - there is a single set of group contributions, no corrections for rings, and no group interactions.

As with all group contribution techniques, the steps for generating an estimate are:

1. dissect the chemical's structure into groups (see code lines 017 through 019)
2. total the contributions for each group (see code lines 024 through 036)
3. insert this contribution total into the model's equation (see code lines 038 and 039)

References:

1. Kevin G. Joback and Robert C. Reid. "Estimation of Pure-Component Properties from Group-Contributions." Chemical Engineering Communications. Volume 57, page 233-243, 1987. (view more)
2. Bruce E. Poling, John M. Prausnitz and John P. O'Connell. "The Properties of Gases and Liquids." The McGraw-Hill Companies, Inc. New York, New York, USA. Edition Fifth, 2001. (view more)

This example estimates the normal boiling point of 3-isopropyl-6-methylene-1-cyclohexene. (Note that the estimation technique distinguishes between acyclic groups and ring groups having the same molecular structure.)

Dissecting this molecular structure into the technique's groups gives the occurrences shown in the table to the right. Multiplying each group's occurrence by its contribution gives the subtotals shown in the table. Adding these subtotals together gives the total shown at the bottom of the table.

Inserting the total of the contributions into the model shown at the top of the page gives an estimate of 445.75K. This is in very good agreement with the reported experimental value of 447.15K.

The figure to the right shows that the estimation technique's errors increase with increasing values of the boiling point. Since boiling point is roughly correlated with molecular weight, we can assume this trend implies that estimation errors will be larger for higher molecular weight chemicals.

The errors shown in the figure begin deviating from the 45 degree reference line at approxmately 350 C. This very approximately corresponds to chemicals having more than 10 carbon atoms. This observation is consistent with the development of the estimation technique, i.e, the technique was developed using a data set consisting mostly of chemicals having between 2 and 10 carbon atoms.

This evaluation was performed on January 30, 2023 using Cranium, Professional Edition version 5.0. The evaluation report can be downloaded by clicking here.

We continue to analyze estimation results to develop additional accuracy rules for Cranium and Synapse. The current rules are shown in the code to the right. (Note that the error value used in the rule was determined after several outliers were removed from the analysis.)

The structure entered above is added to a property estimation request which is sent to an instance of our Cranium, Web Server Edition software product running on a Microsoft Azure virtual machine. Cranium processes the request - dissecting the structure into groups and estimating physical properties. These resulting values are then sent back to this webpage for display.

Click here to learn more about how you can use our Cranium Web Server to distribute your company's physical property data, estimates, and knowledge throughout your organization or contact us for further details.