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

Relative enthalpies of isomers - Comparison of 298.15K enthalpies (kJ mol-1)

Isomers of C6H4

index Species CAS number Name Relative experimental enthalpy (kJ mol-1) sketch
a C6H4 462806 Benzyne 0.0 sketch of Benzyne
b C6H4 16668681 (E)-Hexa-1,5-diyne-3-ene 98.1 sketch of (E)-Hexa-1,5-diyne-3-ene
c C6H4 16668670 (Z)-Hexa-1,5-diyne-3-ene 101.8 sketch of (Z)-Hexa-1,5-diyne-3-ene
The calculated enthalpies include the calculated and scaled vibrational zero-point energy.
Methods with predefined basis sets
semi-empirical AM1 0.0 a
-283.0 b
-280.2 c
PM3 0.0 a
-66.3 b
-62.5 c
PM6 0.0 a
-115.1 b
-110.6 c
MNDOd
484.0 b
484.9 c
composite G1 0.0 a
459.3 b
463.5 c
G2MP2 0.0 a
463.9 b
467.3 c
G2 0.0 a
464.1 b
468.1 c
G3 0.0 a
459.5 b
463.4 c
G3B3 0.0 a
49.2 b
50.9 c
G3MP2 0.0 a
464.0 b
467.3 c
G4 0.0 a
55.3 b
56.4 c
CBS-Q 0.0 a
molecular mechanics MM3
861.8 b
787.8 c

Methods with standard basis sets
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) 6-311+G(3df,2p) cc-pVDZ cc-pVTZ aug-cc-pVDZ aug-cc-pVTZ cc-pV(T+d)Z
hartree fock HF
  b
  c

  b
  c

  b
  c

  b
  c
 
  b
  c
 
  b
  c

  b
  c

  b
  c

NC
NC

  b
  c

  c

  b
  c

  b
  c

NC
density functional LSDA
  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c
 
  b
  c

  b
  c

  b
  c
 
NC
NC
BLYP
  b
  c

  b
  c
 
  b
  c

  b
  c

  b
  c

  b
  c
 
  b
  c

  b
  c
 
  b
  c

  b
  c

NC
NC
 
NC
NC
B1B95
  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c
 
  b
  c

  b
  c

  b
  c
 
NC
NC
B3LYP
  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

NC
NC

  b
  c

  b
  c

  b
  c
 
NC
NC
B3LYPultrafine        
  b
  c
                     
B3PW91
  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  c

  b
  c

  b
  c

  b
  c

  b
  c
 
  b
  c

  b
  c

NC
NC
 
NC
NC
mPW1PW91
  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c
 
  b
  c

  b
  c

NC
NC
 
NC
NC
PBEPBE
  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

NC
NC

  b
  c

  b
  c

NC
NC
 
NC
NC
PBEPBEultrafine        
NC
NC
                     
Moller Plesset perturbation MP2
  b
  c

  b
  c

  b
  c

  b
 
  b
  c
 
  b
  c

  b
  c

  b
  c
 
  b
  c
       
MP2=FULL        
  b
  c
   
  b
  c

  b
  c
             
MP3        
  b
  c
                     

Methods with effective core potentials (select basis sets)
CEP-31G CEP-31G* CEP-121G CEP-121G* LANL2DZ SDD
hartree fock HF
  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c
density functional B1B95
-94330.1 b
-94324.6 c

-94448.8 b
-94443.1 c
       
B3LYP
  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c
Moller Plesset perturbation MP2
  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

  b
  c

Single point energy calculations (select basis sets)
6-311+G(3df,2p) cc-pVDZ cc-pVTZ aug-cc-pVDZ cc-pV(T+d)Z
Moller Plesset perturbation MP2FC// HF/6-31G*  
NC
NC

NC
NC
 
NC
NC
MP2FC// B3LYP/6-31G*  
NC
NC
     
MP2FC// MP2FC/6-31G*
NC

NC
NC

NC
NC

NC
NC

NC
NC
MP4// MP2/6-31G*
NC
       
Coupled Cluster CCSD// MP2FC/6-31G*
NC
 
NC
NC
 
NC
NC
CCSD(T)// MP2FC/6-31G*
NC
 
NC
NC
 
NC
NC
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.