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

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

Isomers of C4H4N2

index Species CAS number Name Relative experimental enthalpy (kJ mol-1) sketch
a C4H4N2 289952 1,3-Diazine 0.0 sketch of 1,3-Diazine
b C4H4N2 290379 Pyrazine 0.1 sketch of Pyrazine
c C4H4N2 110612 Succinonitrile 13.7 sketch of Succinonitrile
d C4H4N2 289805 Pyridazine 82.4 sketch of Pyridazine
The calculated enthalpies include the calculated and scaled vibrational zero-point energy.
Methods with predefined basis sets
semi-empirical AM1 0.0 a
1.3 b
5.7 c
47.7 d
PM3 0.0 a
5.8 b
76.8 c
-110.7 d
PM6 0.0 a
9.9 b
19.4 c
42.6 d
MNDOd 0.0 a
11.7 b
58.3 c
36.1 d
composite G1 0.0 a
16.1 b
-5.2 c
88.7 d
G2MP2 0.0 a
15.5 b
-4.7 c
87.3 d
G2 0.0 a
16.1 b
-5.8 c
88.3 d
G3 0.0 a
16.2 b
-7.4 c
88.2 d
G3B3 0.0 a
18.2 b
9.0 c
92.0 d
G3MP2 0.0 a
15.1 b
-6.1 c
86.5 d
G4 0.0 a
18.0 b
11.8 c
90.8 d
Group additivity gaw
188.0 c
molecular mechanics MM3 0.0 a
0.6 b
10.5 c
84.0 d

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 0.0 a
11.4 b
-13.0 c
64.4 d
0.0 a
22.4 b
-48.7 c
119.3 d
0.0 a
22.4 b
-48.7 c
119.3 d
0.0 a
18.8 b
-4.4 c
102.8 d
  0.0 a
26.4 b
5.3 c
111.5 d
  0.0 a
27.3 b
-11.0 c
112.8 d
0.0 a
27.1 b
-7.8 c
112.3 d
0.0 a
27.1 b
2.1 c
110.9 d
0.0 a
27.1 b
-1.0 c
112.9 d
0.0 a
26.6 b
4.4 c
110.6 d
0.0 a
27.2 b
-1.4 c
110.8 d
0.0 a
26.3 b
6.6 c
110.2 d
0.0 a
27.2 b
-1.3 c
111.2 d
0.0 a
27.2 b
-1.4 c
110.8 d
density functional LSDA 0.0 a
12.1 b
137.3 c
52.2 d
0.0 a
15.4 b
72.9 c
100.5 d
0.0 a
15.4 b
72.9 c
100.5 d
0.0 a
13.5 b
109.7 c
89.6 d
0.0 a
15.6 b
135.7 c
91.4 d
0.0 a
15.5 b
135.6 c
90.7 d
0.0 a
15.6 b
133.3 c
90.4 d
0.0 a
16.5 b
110.0 c
93.8 d
0.0 a
16.5 b
113.2 c
92.9 d
0.0 a
15.5 b
138.9 c
90.2 d
  0.0 a
15.5 b
135.6 c
89.4 d
0.0 a
15.8 b
121.6 c
90.1 d
0.0 a
14.7 b
136.3 c
89.3 d
  0.0 a
15.8 b
121.6 c
90.1 d
BLYP 0.0 a
11.1 b
55.1 c
44.4 d
0.0 a
13.8 b
-10.7 c
88.9 d

NC
0.0 a
12.2 b
27.3 c
80.8 d
0.0 a
14.3 b
48.3 c
85.8 d
0.0 a
14.2 b
48.4 c
85.1 d
0.0 a
14.4 b
45.6 c
85.4 d

NC
0.0 a
15.0 b
27.2 c
86.5 d
0.0 a
14.1 b
47.8 c
85.3 d
  0.0 a
14.0 b
47.9 c
83.3 d
0.0 a
14.6 b
31.3 c
85.2 d
0.0 a
13.6 b
46.2 c
83.6 d
  0.0 a
14.6 b
31.3 c
85.2 d
B1B95 0.0 a
11.1 b
59.9 c
53.7 d
0.0 a
16.4 b
4.0 c
100.7 d
0.0 a
16.4 b
4.0 c
100.7 d
0.0 a
13.7 b
40.9 c
89.1 d
0.0 a
17.5 b
64.3 c
94.8 d
0.0 a
17.0 b
64.3 c
93.3 d
0.0 a
17.1 b
63.5 c
93.3 d
0.0 a
17.8 b
45.2 c
95.9 d
0.0 a
17.8 b
48.1 c
95.0 d
0.0 a
16.9 b
65.1 c
93.0 d
  0.0 a
17.1 b
64.0 c
92.1 d
0.0 a
17.7 b
55.6 c
93.7 d
0.0 a
16.8 b
65.7 c
92.5 d
  0.0 a
17.7 b
55.6 c
93.7 d
B3LYP 0.0 a
10.9 b
55.3 c
51.3 d
0.0 a
15.4 b
-5.7 c
98.1 d
0.0 a
15.4 b
-5.7 c
98.1 d
0.0 a
13.3 b
34.7 c
87.5 d
0.0 a
16.4 b
55.0 c
92.6 d
0.0 a
16.3 b
55.3 c
92.0 d
0.0 a
16.5 b
54.0 c
92.1 d
0.0 a
17.1 b
32.7 c
94.2 d
0.0 a
17.1 b
35.6 c
93.4 d
0.0 a
16.3 b
54.6 c
91.8 d
0.0 a
16.5 b
42.7 c
93.4 d
0.0 a
16.1 b
54.5 c
90.1 d
0.0 a
16.8 b
40.8 c
91.8 d
0.0 a
15.8 b
54.7 c
90.4 d
  0.0 a
16.8 b
40.8 c
91.8 d
B3LYPultrafine         0.0 a
16.4 b
54.9 c
92.6 d
                     
B3PW91 0.0 a
11.3 b
64.0 c
52.1 d
0.0 a
16.6 b
8.2 c
99.4 d
0.0 a
16.5 b
8.2 c
99.4 d
0.0 a
13.9 b
46.3 c
87.9 d
0.0 a
17.2 b
69.2 c
92.5 d
0.0 a
17.1 b
69.7 c
91.9 d
0.0 a
17.1 b
69.5 c
91.9 d
0.0 a
18.0 b
94.6 d
0.0 a
17.9 b
53.7 c
93.7 d
0.0 a
17.0 b
69.7 c
91.5 d
  0.0 a
17.1 b
69.5 c
90.6 d
0.0 a
17.4 b
58.8 c
91.5 d
0.0 a
16.5 b
70.7 c
90.3 d
  0.0 a
17.4 b
58.8 c
91.5 d
mPW1PW91 0.0 a
11.3 b
67.4 c
53.4 d
0.0 a
17.0 b
13.3 c
101.3 d
0.0 a
17.0 b
13.2 c
101.4 d
0.0 a
14.3 b
51.1 c
89.2 d
0.0 a
17.8 b
73.6 c
93.9 d
0.0 a
17.7 b
74.1 c
93.2 d
0.0 a
17.7 b
73.9 c
93.2 d
0.0 a
18.5 b
55.5 c
95.9 d
0.0 a
18.5 b
58.3 c
95.0 d
0.0 a
17.6 b
73.8 c
92.8 d
  0.0 a
17.7 b
74.2 c
92.0 d
0.0 a
22.7 b
63.4 c
92.7 d
0.0 a
17.1 b
74.9 c
91.6 d
  0.0 a
22.7 b
63.4 c
92.7 d
PBEPBE 0.0 a
11.6 b
77.4 c
46.7 d
0.0 a
15.0 b
15.9 c
91.6 d
0.0 a
15.0 b
15.9 c
91.7 d
0.0 a
12.9 b
50.2 c
81.8 d
0.0 a
15.1 b
74.9 c
85.9 d
0.0 a
15.0 b
75.2 c
85.2 d
0.0 a
15.1 b
73.1 c
85.2 d
0.0 a
15.9 b
55.4 c
87.9 d
0.0 a
15.9 b
58.3 c
87.0 d
0.0 a
14.8 b
75.8 c
85.0 d
0.0 a
15.2 b
65.0 c
86.7 d
0.0 a
15.0 b
75.3 c
83.9 d
0.0 a
15.3 b
63.2 c
85.0 d
0.0 a
14.4 b
75.2 c
83.4 d
  0.0 a
15.3 b
63.2 c
85.0 d
Moller Plesset perturbation MP2 0.0 a
10.7 b
-175.5 c
48.8 d
0.0 a
16.6 b
-121.3 c
90.1 d
0.0 a
16.6 b
-121.3 c
90.1 d
0.0 a
12.8 b
-88.3 c
79.2 d
  0.0 a
14.6 b
1.4 c
89.1 d
  0.0 a
14.7 b
-12.1 c
90.1 d
0.0 a
14.3 b
-10.4 c
90.1 d
0.0 a
15.2 b
15.3 c
90.3 d
  0.0 a
14.4 b
0.3 c
88.7 d
0.0 a
14.6 b
89.7 d
    0.0 a
14.6 b
89.7 d
MP2=FULL  
NC

NC

NC
0.0 a
14.8 b
1.8 c
90.1 d

NC

NC
0.0 a
14.7 b
-11.1 c
90.4 d
0.0 a
14.3 b
-9.4 c
90.4 d
   
NC

NC
   
NC
MP3         0.0 a
16.3 b
19.0 c
92.7 d
                     
MP4  
NC
                           
Configuration interaction CID  
NC

NC

NC

NC

NC

NC

NC
     
NC
       
CISD  
NC

NC

NC

NC

NC

NC

NC
     
NC
       
Quadratic configuration interaction QCISD  
NC
NC

NC

NC

NC
0.0 a
19.0 b
-2.0 c
94.8 d
0.0 a
19.0 b
3.7 c
95.6 d

NC
0.0 a
19.3 b
-16.2 c
95.7 d
   
NC
       
Coupled Cluster CCD  
NC

NC

NC

NC

NC

NC

NC
     
NC
       

Methods with effective core potentials (select basis sets)
CEP-31G CEP-31G* CEP-121G CEP-121G* LANL2DZ SDD
hartree fock HF 0.0 a
20.9 b
9.4 c
105.2 d
0.0 a
29.0 b
20.7 c
119.7 d
0.0 a
18.3 b
3.1 c
99.4 d
0.0 a
26.8 b
-3.0 c
113.4 d
0.0 a
19.1 b
1.0 c
98.1 d
0.0 a
19.2 b
0.6 c
98.0 d
density functional B1B95 0.0 a
16.4 b
61.3 c
97.2 d
0.0 a
19.8 b
89.1 c
106.0 d
       
B3LYP 0.0 a
16.3 b
48.0 c
92.4 d
0.0 a
19.7 b
70.7 c
102.3 d
0.0 a
13.1 b
44.8 c
85.6 d
0.0 a
16.9 b
52.3 c
95.2 d
0.0 a
14.4 b
47.0 c
87.8 d
0.0 a
14.4 b
47.4 c
87.9 d
Moller Plesset perturbation MP2 0.0 a
15.0 b
-86.2 c
79.9 d
0.0 a
17.2 b
6.7 c
96.0 d
0.0 a
13.2 b
-84.4 c
72.8 d
0.0 a
15.9 b
1.5 c
89.7 d
0.0 a
14.3 b
-95.4 c
77.0 d
0.0 a
14.4 b
-96.1 c
76.7 d

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*   0.0 a
-34.3 b
-48.6 c
82.1 d
0.0 a
-25.8 b
-32.4 c
81.6 d
  0.0 a
-25.8 b
-32.4 c
81.6 d
MP2FC// B3LYP/6-31G*   0.0 a
15.0 b
7.9 c
89.5 d
     
MP2FC// MP2FC/6-31G*
NC
NC
0.0 a
14.6 b
1.4 c
88.5 d
0.0 a
14.6 b
16.0 c
89.2 d
0.0 a
13.2 b
9.6 c
87.2 d
0.0 a
14.6 b
16.0 c
89.2 d
MP4// MP2/6-31G*
NC
NC
       
Coupled Cluster CCSD// HF/6-31G*    
NC
NC
 
NC
NC
CCSD(T)// HF/6-31G*    
NC
NC
 
NC
NC
CCSD// MP2FC/6-31G*
NC
NC

NC
0.0 a
20.1 b
11.7 c
96.3 d
  0.0 a
20.1 b
11.7 c
96.3 d
CCSD(T)// MP2FC/6-31G*
NC
NC

NC
0.0 a
19.0 b
19.3 c
92.2 d
  0.0 a
19.0 b
19.3 c
92.2 d
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.