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Joback method

The Joback method[1] (often named JobackReid

method) predicts eleven important and commonly used

pure component thermodynamic properties from molec-

ular structure only

1 Basic Principles

11 Group Contribution Method

Principle of a Group Contribution Method

The Joback method is a group contribution method

These kind of methods use basic structural information

of a chemical molecule like a list of simple functional

groups adds parameters to these functional groups and

calculates thermophysical and transport properties as afunction of the sum of group parameters

Joback assumes that there are no interactions between

the groups and therefore only uses additive contributions

and no contributions for interactions between groups

Other group contribution methods especially methods

like UNIFAC which estimate mixture properties like ac-

tivity coefficients use both simple additive group param-

eters and group interaction parameters The big advan-

tage of using only simple group parameters is the small

number of needed parameters The number of needed

group interaction parameters gets very high for an in-

creasing number of groups (1 for two groups 3 for threegroups 6 for four groups 45 for ten groups and twice as

much if the interactions are not symmetric)

Nine of the properties are single temperature-

independent values mostly estimated by a simple

sum of group contribution plus an addend Two of

the estimated properties are temperature-dependent

the ideal gas heat capacity and the dynamic viscosity

of liquids The heat capacity polynomial uses four

parameters and the viscosity equation only 2 In both

cases the equation parameters are calculated by group

contributions

12 History

The Joback method is an extension of the Lydersen

method[2] and uses very similar groups formulas and

parameters for the three properties the Lydersen already

supported (critical temperature critical pressure critical

volume)

Joback extended the range of supported properties cre-

ated new parameters and modified slightly the formulas

of the old Lydersen method

2 Model Strengths and Weak-

nesses

21 Strengths

The popularity and success of the Joback method mainly

originates from the single group list for all properties

This allows one to get all eleven supported properties

from a single analysis of the molecular structure

The Joback method additionally uses a very simple and

easy to assign group scheme which makes the methodusable also for people with only basic chemical knowl-

edge

22 Weaknesses

Newer developments of estimation methods[3][4] have

shown that the quality of the Joback method is limited

The original authors already stated themselves in the orig-

inal paper ldquoHigh accuracy is not claimed but the pro-

posed method are often as or more accurate than tech-

niques in common use todayrdquoThe list of groups dont cover many common molecules

sufficiently Especially aromatic compounds are not

1

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2 3 FORMULAS

Systematic Errors of the Joback Method (Normal Boiling Point)

differentiated from normal ring containing components

This is a severe problem because aromatic and aliphaticcomponents differ strongly

The data base Joback and Reid used for obtaining the

group parameters was rather small and covered only a

limited number of different molecules The best cov-

erage has been achieved for normal boiling points (438

components) and the worst for heat of fusion (155 com-

ponents) Current developments that can use data banks

like the Dortmund Data Bank or the DIPPR data base

have a much broader coverage

The formula used for the prediction of the normal boil-

ing point shows another problem Joback assumed a con-

stant contribution of added groups in homologous serieslike the alkanes This doesnt describe the real behavior

of the normal boiling points correctly[5] Instead of the

constant contribution a decrease of the contribution with

increasing number of groups must be applied The cho-

sen formula of the Joback method leads to high deviations

for large and small molecules and an acceptable good es-

timation only for mid-sized components

3 Formulas

In the following formulas Gᵢ denotes a group contribution

Gᵢ are counted for every single available group If a group

is present multiple times each occurrence is counted sep-

arately

31 Normal Boiling Point

T b = 198 + sum

T bi

32 Melting Point

T m = 1225 + sum

T mi

33 Critical Temperature

T c = T b

9831310584 + 0965

sumT ci minus (

sumT ci)

2983133minus1

This critical temperature equation needs a normal boiling

point T If an experimental value is available it is recom-

mended to use this boiling point It is on the other handalso possible to input the normal boiling point estimated

by the Joback method This will lead to a higher error

34 Critical Pressure

P c = [0113 + 00032 lowast N A minus

sumP ci]

minus2

NA Number of atoms in the molecular structure (includ-

ing hydrogens)

35 Critical Volume

V c = 175 + sum

V ci

36 Heat of Formation (Ideal Gas 298 K)

H formation = 6829 + sum

H formi

37 Gibbs Energy of Formation (Ideal Gas

298 K)

Gformation = 5388 + sum

Gformi

38 Heat Capacity (Ideal Gas)

C P = sum

ai minus 379 3 + [sum

bi + 0210]T +1048667sumci minus 391 middot 10minus4

1048669T 2 +

1048667sumdi + 206 middot 10minus7

1048669T 3

The Joback method uses a four parameter polynomial to

describe the temperature dependency of the ideal gas heat

capacity These parameters are valid from 273 K to ap-

prox 1000 K

39 Heat of Vaporization at Normal Boil-

ing Point

∆H vap = 1530 + sum

H vapi

310 Heat of Fusion

∆H fus = minus088 + sum

H fusi

311 Liquid Dynamic Viscosity

ηL = M we[sum

ηaminus59782]T +sum

ηbminus11202

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3

M Molecular Weight

The method uses a two parameter equation to describe

the temperature dependency of the dynamic viscosity

The authors state that the parameters are valid from the

melting temperature up to 07 of the critical temperature

(Tᵣlt07)

4 Group Contributions

5 Example Calculation

Acetone (Propanone) is the simplest ketone and is sepa-

rated into three groups in the Joback method two methyl

groups (-CH3) and one ketone group (C=O) Since the

methyl group is present twice its contributions have to

be added twice

6 References

[1] Joback KG Reid RC ldquoEstimation of Pure-Component

Properties from Group-Contributionsrdquo Chem Eng Com-

mun 57 233ndash243 1987

[2] Lydersen AL ldquoEstimation of Critical Properties of Or-

ganic Compoundsrdquo University of Wisconsin College En-

gineering Eng Exp Stn Rep 3 Madison Wisconsin

1955

[3] Constantinou L Gani R ldquoNew Group Contribution

Method for Estimating Properties of Pure Compoundsrdquo

AIChE J 40(10) 1697ndash1710 1994

[4] Nannoolal Y Rarey J Ramjugernath J ldquoEstimation of

pure component properties Part 2 Estimation of critical

property data by group contributionrdquo Fluid Phase Equi-

lib 252(1ndash2) 1ndash27 2007

[5] Stein SE Brown RL ldquoEstimation of Normal Boiling

Points from Group Contributionsrdquo J Chem Inf Comput

Sci 34 581ndash587 (1994)

7 External links

bull Online property estimation with the Joback method

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