return to home page

IV.A.4. (XIV.F.)

Relative enthalpies of isomers - Comparison of 0K enthalpies (kJ mol-1)

Isomers of C8H18

index Species CAS number Name Relative experimental enthalpy (kJ mol-1) sketch
a C8H18 111659 Octane   sketch of Octane
b (CH3)3CC(CH3)3 594821 tetramethylbutane   sketch of tetramethylbutane
The calculated enthalpies include the calculated and scaled vibrational zero-point energy.
Methods with predefined basis sets
Methods with standard basis sets
3-21G 6-31G* 6-31+G** TZVP
hartree fock HF       0.0 a
40.7 b
density functional SVWN 0.0 a
-45.5 b 		0.0 a
-21.9 b 		0.0 a
-22.5 b 		 
B3LYP       0.0 a
26.8 b
M06-2X   0.0 a
-10.1 b 		   
HSEh1PBE   0.0 a
662.7 b 		   
Moller Plesset perturbation MP2FC       0.0 a
-28.1 b
B2PLYP   0.0 a
11.6 b 		0.0 a
9.0 b 		 
NC = not calculated
For descriptions of the methods (AM1, HF, MP2, ...) and basis sets (3-21G, 3-21G*, 6-31G, ...) see the glossary in section I.C. Predefined means the basis set used is determined by the method.
gaw refers to the group additivity method implemeted in the NIST Chemistry Webbook.

See section III.C.1 List or set vibrational scaling factors to change the scale factors used here.
See section III.C.2 Calculate a vibrational scaling factor for a given set of molecules to determine the least squares best scaling factor.