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

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

Isomers of C3H8N2O

index Species CAS number Name Relative experimental enthalpy (kJ mol-1) sketch
a NH2CONHC2H5 625525 Urea, ethyl- 0.0 sketch of Urea, ethyl-
b NH(CH3)CONH(CH3) 96311 Urea, N,N'-dimethyl- 35.9 sketch of Urea, N,N'-dimethyl-
c N(CH3)2CONH2 598947 Urea, N,N-dimethyl- 37.5 sketch of Urea, N,N-dimethyl-
The calculated enthalpies include the calculated and scaled vibrational zero-point energy.
Methods with predefined basis sets
semi-empirical AM1 0.0 a
45.5 b
51.9 c
PM3 0.0 a
18.7 b
20.5 c
PM6 0.0 a
28.1 b
28.3 c
MNDOd 0.0 a
23.7 b
44.0 c
composite G1 0.0 a
21.4 b
19.7 c
G2MP2 0.0 a
22.2 b
21.4 c
G2 0.0 a
22.5 b
21.6 c
G3 0.0 a
23.3 b
22.4 c
G3B3 0.0 a
25.6 b
26.0 c
G3MP2 0.0 a
24.2 b
22.9 c
G4 0.0 a
27.2 b
27.0 c
molecular mechanics DREIDING 0.0 a
MM3 0.0 a
35.6 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 0.0 a
3.3 b
8.9 c
0.0 a
12.5 b
20.1 c
0.0 a
12.5 b
20.1 c
0.0 a
28.4 b
35.4 c
  0.0 a
22.0 b
32.3 c
  0.0 a
19.4 b
28.8 c
0.0 a
22.8 b
33.0 c
0.0 a
20.4 b
30.3 c
0.0 a
23.8 b
34.4 c
0.0 a
20.8 b
31.4 c
0.0 a
24.5 b
34.5 c
0.0 a
26.9 b
37.1 c
0.0 a
24.9 b
35.4 c
0.0 a
24.5 b
34.5 c
density functional LSDA 0.0 a
-6.3 b
-6.1 c
0.0 a
3.0 b
5.5 c
0.0 a
3.0 b
5.5 c
0.0 a
18.9 b
18.0 c
0.0 a
12.6 b
8.7 c
0.0 a
17.1 b
13.9 c
0.0 a
25.6 b
21.2 c
0.0 a
19.5 b
14.7 c
0.0 a
21.6 b
18.1 c
0.0 a
15.6 b
11.5 c
  0.0 a
17.7 b
14.0 c
0.0 a
24.6 b
20.2 c
0.0 a
27.7 b
22.2 c
  0.0 a
24.6 b
20.2 c
BLYP 0.0 a
-3.0 b
0.5 c
0.0 a
2.0 b
9.8 c
  0.0 a
19.0 b
23.4 c
0.0 a
12.3 b
0.0 a
17.3 b
20.4 c
0.0 a
24.6 b
28.6 c
  0.0 a
21.1 b
24.4 c
0.0 a
16.3 b
18.0 c
  0.0 a
19.2 b
21.6 c
0.0 a
23.7 b
26.5 c
0.0 a
28.0 b
29.9 c
  0.0 a
23.7 b
26.5 c
B1B95 0.0 a
0.8 b
3.0 c
0.0 a
8.1 b
13.2 c
0.0 a
8.1 b
13.2 c
0.0 a
22.4 b
26.5 c
0.0 a
15.6 b
17.3 c
0.0 a
21.0 b
22.5 c
0.0 a
27.1 b
27.8 c
0.0 a
20.5 b
20.8 c
0.0 a
23.9 b
24.8 c
0.0 a
19.8 b
20.1 c
  0.0 a
21.3 b
22.4 c
0.0 a
25.8 b
26.7 c
0.0 a
30.0 b
29.8 c
  0.0 a
25.8 b
26.7 c
B3LYP 0.0 a
-1.1 b
2.5 c
0.0 a
5.6 b
13.0 c
0.0 a
5.6 b
13.0 c
0.0 a
21.8 b
26.4 c
0.0 a
14.0 b
17.5 c
0.0 a
19.2 b
22.9 c
0.0 a
25.6 b
29.2 c
0.0 a
19.5 b
22.1 c
0.0 a
22.6 b
26.1 c
0.0 a
18.2 b
20.7 c
0.0 a
25.2 b
28.8 c
0.0 a
20.5 b
23.6 c
0.0 a
25.0 b
28.0 c
0.0 a
28.6 b
31.1 c
  0.0 a
25.0 b
28.0 c
B3LYPultrafine         0.0 a
13.9 b
17.5 c
                     
B3PW91 0.0 a
1.5 b
5.6 c
0.0 a
10.3 b
16.6 c
0.0 a
10.3 b
16.6 c
0.0 a
23.8 b
28.2 c
0.0 a
16.4 b
19.5 c
0.0 a
21.6 b
24.8 c
0.0 a
27.3 b
29.8 c
0.0 a
21.5 b
23.3 c
0.0 a
24.5 b
27.1 c
0.0 a
20.4 b
22.6 c
  0.0 a
21.7 b
24.4 c
0.0 a
26.6 b
28.8 c
0.0 a
29.5 b
31.2 c
  0.0 a
26.6 b
28.8 c
mPW1PW91 0.0 a
1.9 b
5.4 c
0.0 a
10.5 b
16.2 c
0.0 a
10.6 b
16.4 c
0.0 a
24.4 b
28.3 c
0.0 a
16.7 b
19.4 c
0.0 a
22.0 b
24.8 c
0.0 a
27.9 b
29.8 c
0.0 a
21.7 b
23.0 c
0.0 a
24.8 b
27.0 c
0.0 a
20.8 b
22.7 c
  0.0 a
21.9 b
24.2 c
0.0 a
27.1 b
28.8 c
0.0 a
30.0 b
31.2 c
  0.0 a
27.1 b
28.8 c
PBEPBE 0.0 a
2.5 b
4.3 c
0.0 a
6.1 b
11.4 c
0.0 a
6.1 b
11.4 c
0.0 a
21.7 b
24.5 c
0.0 a
15.5 b
15.9 c
0.0 a
20.5 b
21.2 c
0.0 a
27.8 b
27.9 c
0.0 a
21.0 b
20.5 c
0.0 a
23.9 b
24.3 c
0.0 a
19.3 b
19.0 c
0.0 a
27.4 b
27.4 c
0.0 a
21.2 b
21.3 c
0.0 a
26.7 b
26.4 c
0.0 a
30.3 b
29.3 c
  0.0 a
26.7 b
26.4 c
PBEPBEultrafine         0.0 a
15.5 b
15.9 c
                     
Moller Plesset perturbation MP2 0.0 a
3.0 b
3.1 c
0.0 a
14.2 b
14.8 c
0.0 a
14.2 b
14.8 c
0.0 a
29.3 b
28.9 c
  0.0 a
23.7 b
24.2 c
  0.0 a
25.7 b
24.8 c
0.0 a
28.4 b
28.2 c
0.0 a
23.8 b
21.2 c
  0.0 a
26.2 b
25.4 c
       
MP2=FULL         0.0 a
19.7 b
20.6 c
    0.0 a
25.8 b
24.8 c
0.0 a
28.6 b
28.2 c
             
MP3         0.0 a
20.7 b
24.7 c
                     

Methods with effective core potentials (select basis sets)
CEP-31G CEP-31G* CEP-121G CEP-121G* LANL2DZ SDD
hartree fock HF 0.0 a
27.5 b
35.6 c
0.0 a
16.6 b
26.2 c
0.0 a
31.6 b
37.8 c
0.0 a
20.4 b
29.4 c
0.0 a
32.2 b
38.3 c
0.0 a
32.5 b
38.5 c
density functional B1B95 0.0 a
26.4 b
28.3 c
0.0 a
20.2 b
20.1 c
       
B3LYP 0.0 a
24.2 b
27.3 c
0.0 a
17.6 b
19.0 c
0.0 a
26.8 b
29.0 c
0.0 a
20.7 b
22.2 c
0.0 a
27.3 b
29.4 c
0.0 a
27.3 b
29.4 c
Moller Plesset perturbation MP2 0.0 a
31.8 b
30.2 c
0.0 a
23.4 b
21.8 c
0.0 a
33.5 b
30.2 c
0.0 a
26.2 b
23.1 c
0.0 a
34.6 b
30.9 c
0.0 a
34.8 b
31.0 c

Single point energy calculations (select basis sets)
cc-pVDZ cc-pVTZ aug-cc-pVDZ cc-pV(T+d)Z
Moller Plesset perturbation MP2FC// HF/6-31G* 0.0 a
-9.1 b
26.0 c
0.0 a
-16.9 b
24.7 c
  0.0 a
-16.9 b
24.7 c
MP2FC// B3LYP/6-31G* 0.0 a
26.3 b
25.1 c
     
MP2FC// MP2FC/6-31G*     0.0 a
31.1 b
29.5 c
 
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.