Lydersen method

The Lydersen method is a group contribution method for estimating the critical quantities , and . The Lydersen method is the model for many newer models according to Joback , Ambrose, Constantinou and Gani u. a. When estimating the critical temperature, the Lydersen method is based on Guldberg's rule , which relates the critical temperature to the normal boiling point. ${\displaystyle T_{\text{c}}}$ ${\displaystyle P_{\text{c}}}$ ${\displaystyle V_{\text{c}}}$

Determining equations

• Critical temperature:

  ${\displaystyle T_{\text{c}}={\frac {T_{\text{b}}}{0{,}567+\sum G_{\text{i}}-\left(\sum G_{\text{i}}\right)^{2}}}}$

• Critical pressure:

  ${\displaystyle P_{\text{c}}={\frac {M}{\left(0{,}34+\sum G_{\text{i}}\right)^{2}}}}$

• Critical Volume:

  ${\displaystyle V_{\text{c}}=40+\sum G_{\text{i}}}$

${\displaystyle T_{\text{b}}}$is the normal boiling point , the molar mass , are group contributions (different for the individual sizes) for functional groups of a molecule . ${\displaystyle M}$ ${\displaystyle G_{\text{i}}}$

Group contributions

group	G i (T c )	G i (P c )	G i (V c )		group	G i (T c )	G i (P c )	G i (V c )
-CH 3 , -CH 2 -	0.020	0.227	55.0		> CH	0.012	0.210	51.0
–C <	-	0.210	41.0		= CH 2 , = CH	0.018	0.198	45.0
= C <, = C =	-	0.198	36.0		= C – H, = C–	0.005	0.153	36.0
–CH 2 - (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 (aromatic)	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		-NH 2	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		-NO 2	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	-	-

Sample calculation

Acetone breaks down into two different fragments, a carbonyl group and two methyl groups. The following calculation results for the critical volume:

${\displaystyle V_{\text{c}}=40+60{,}0+2\cdot 55{,}0=210~\mathrm {cm^{3}} }$

Values ​​of 215.90 cm ³ , 230.5 cm ³ and 209.0 cm ³ can be found in the literature .

Individual evidence

1. ↑ Lydersen aL, "Estimation of Critical Properties of Organic Compounds", University of wisconsin College Engineering, Eng. Exp. Stn. Rep. 3, Madison, Wisconsin
2. ↑ K. G Joback, R. C Reid: Estimation of pure-component properties from group-contributions . In: Chemical Engineering Communications . tape 57 , no. 1 , 1987, pp. 233-243 .
3. ↑ D. Ambrose, Teddington (England). Div. of Chemical Standards National Physical Lab .: Correlation and estimation of vapor-liquid critical properties. Part 1: Critical temperatures of organic compounds . Rep.No. 92. National Physical Lab., Teddington (England). Div. of Chemical Standards, 1978, p. 1-35 .
4. ↑ Leonidas Constantinou, Rafiqul Gani: New group contribution method for estimating properties of pure compounds . In: AIChE Journal . tape 40 , no. 10 , October 1994, p. 1697-1710 , doi : 10.1002 / aic.690401011 .
5. ↑ Dortmund database
6. ↑ AN Campbell, RM Chatterjee: The critical constants and orthobaric densities of acetone, chloroform, benzene, and carbon tetrachloride . In: Canadian Journal of Chemistry . tape 47 , no. 20 , October 15, 1969, p. 3893-3898 , doi : 10.1139 / v69-646 .
7. ^ W. Herz, E. Neukirch: On Knowledge of the Critical State . In: Z.Phys.Chem. (Leipzig) . tape 104 , 1923, pp. 433-450 .
8. ↑ Kenneth A. Kobe, Horace R. Crawford, Robert W. Stephenson: Industrial Design Data - Critical Properties and Vapor Presesures of Some Ketones . In: Industrial & Engineering Chemistry . tape 47 , no. 9 , September 1955, p. 1767-1772 , doi : 10.1021 / ie50549a025 .