I Lab Services 

4.16 Boiling Point 

This module calculates the boiling point values for compounds, from 0.001 torr to 7,600 torr.  The 

predictions are normally accurate to within 

 5 C for structures with fewer than two polar groups, 

and to within 

10 C for structures with more polar groups. 

To determine constants and relationships, the algorithm uses an internal database which 

contains boiling points for 10,000 compounds 6,000 of which have a boiling point at 

760 mmHg.  Additive increments of atoms and groups, force increments of interactions between 

groups and atoms are calculated from this database.  These database values are also used to 

evaluate and fine tune the specialized algorithms for ACD/Boiling Point & Vapor Pressure 

Calculator.  Your compound does not have to be in the database in order to have its boiling point 

calculated! 

Prior to calculation, you should select units for pressure and temperature, and specify pressure at 

which the boiling point value is to be calculated. 

The resultant dialog box contains structure, boiling point value, and pressure at which it was 

calculated.  All of this data can be printed at once by clicking Print or you may wish to edit the 

default report page in the ChemSketch and then print it (click Insert to start editing). 

4.16.1 Limitations 

Restrictions are: 

A maximum of 255 atoms excluding hydrogen can be calculated; and 

Only C, H, O, S, P, N, F, Cl, Br, I, Se, Si, Ge, Pb, Sn, As, and B are permitted elements. 

4.16.2  What is Boiling Point? 

The boiling point of a pure substance is in principle a non additive property.  It has been 

observed experimentally that in homologous sets, the dependence of boiling point on the number 

of CH

2

  groups obeys, approximately, the following non linear function:  

a

n

a

1

(1)

C

0

bp

a

2

where n

c

 is the number of CH

2

  groups in the structure, bp is the observed boiling point, and a

i

are empirically determined constants.  Note, however, that the additive algorithm cannot be 

applied to prediction of the boiling point.   

We have made a detailed comparison of the behavior of different macroscopic properties, such 

as the index of refraction (nd

20

), density (d

20

), and surface tension (

), for different homologous 

sets, with respect to boiling point.  We observed that all of these properties can be approximately 

described by Equation (1).  These three properties are further related by different relationships 

between two out of four macroscopic properties (molar volume, molecular weight, molar 

refractivity, and the parachor): 

nd

20

 = f(MR, MV) 

d

20

 = f(MW, MV) 

 = f(parachor, MV).   

ACD/I Lab via ChemSketch  

User's Guide 

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