Hubbry Logo
search
search button
Sign in
Historyarrow-down
starMorearrow-down
Hubbry Logo
search
search button
Sign in
Lydersen method
Community hub for the Wikipedia article
logoWikipedian hub
Welcome to the community hub built on top of the Lydersen method Wikipedia article. Here, you can discuss, collect, and organize anything related to Lydersen method. The purpose of the hub is to connect people, foster deeper knowledge, and help improve the root Wikipedia article.
Add your contribution
Inside this hub
Lydersen method

The Lydersen method is a group contribution method for the estimation of critical properties temperature (Tc), pressure (Pc) and volume (Vc). The method is named after Aksel Lydersen who published it in 1955.[1] The Lydersen method is the prototype for and ancestor of many new models like Joback,[2] Klincewicz,[3] Ambrose,[4] Gani-Constantinou[5] and others.

The Lydersen method is based in case of the critical temperature on the Guldberg rule which establishes a relation between the normal boiling point and the critical temperature.

Equations

[edit]

Critical temperature

[edit]

Guldberg has found that a rough estimate of the normal boiling point Tb, when expressed in kelvins (i.e., as an absolute temperature), is approximately two-thirds of the critical temperature Tc. Lydersen uses this basic idea but calculates more accurate values.

Critical pressure

[edit]

Critical volume

[edit]

M is the molar mass and Gi are the group contributions (different for all three properties) for functional groups of a molecule.

Group contributions

[edit]
Group Gi (Tc) Gi (Pc) Gi (Vc) Group Gi (Tc) Gi (Pc) Gi (Vc)
-CH3,-CH2- 0.020 0.227 55.0 >CH 0.012 0.210 51.0
-C< - 0,210 41.0 =CH2,#CH 0.018 0,198 45.0
=C<,=C= - 0.198 36.0 =C-H,#C- 0.005 0.153 36.0
-CH2-(Ring) 0.013 0.184 44.5 >CH-(Ring) 0.012 0.192 46.0
>C<(Ring) -0.007 0.154 31.0 =CH-,=C<,=C=(Ring) 0.011 0.154 37.0
-F 0.018 0.224 18.0 -Cl 0.017 0.320 49.0
-Br 0.010 0.500 70.0 -I 0.012 0.830 95.0
-OH 0.082 0.060 18.0 -OH(Aromat) 0.031 -0.020 3.0
-O- 0.021 0.160 20.0 -O-(Ring) 0.014 0.120 8.0
>C=O 0.040 0.290 60.0 >C=O(Ring) 0.033 0.200 50.0
HC=O- 0.048 0.330 73.0 -COOH 0.085 0.400 80.0
-COO- 0.047 0.470 80.0 -NH2 0.031 0.095 28.0
>NH 0.031 0.135 37.0 >NH(Ring) 0.024 0.090 27.0
>N 0.014 0.170 42.0 >N-(Ring) 0.007 0.130 32.0
-CN 0.060 0.360 80.0 -NO2 0.055 0.420 78.0
-SH,-S- 0.015 0.270 55.0 -S-(Ring) 0.008 0.240 45.0
=S 0.003 0.240 47.0 >Si< 0.030 0.540 -
-B< 0.030 - -

Example calculation

[edit]

Group assignment for Acetone

Acetone is fragmented in two different groups, one carbonyl group and two methyl groups. For the critical volume the following calculation results:

Vc = 40 + 60.0 + 2 * 55.0 = 210 cm3

In the literature (such as in the Dortmund Data Bank) the values 215.90 cm3,[6] 230.5 cm3 [7] and 209.0 cm3 [8] are published.

References

[edit]
Add your contribution
Related Hubs