Computational Chemistry Comparison and Benchmark DataBase Release 22 (May 2022) Standard Reference Database 101 National Institute of Standards and Technology
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Tautomer energy comparison

using model chemistry: HF/3-21G

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			-12	-7	allene	propyne	-5
C4H6			-5	3	1,2-Butadiene	1-Butyne	-8
C4H6			-30	-17	1,2-Butadiene	2-Butyne	-13
C4H6			-44	-51	1,2-Butadiene	1,3-Butadiene	8
C4H6			-78	-49	Cyclobutene	1,3-Butadiene	-29
C4H6			-136	-82	1-Methylcyclopropene	1,2-Butadiene	-53
C4H6			72	42	Methylenecyclopropane	1-Methylcyclopropene	30
C3H6O			-108	-110	Oxetane	Propanal	2
C4H8			-36	-33	cyclobutane	1-Butene	-3
C3H4O2			62	29	2-Propenoic acid	β–Propiolactone	33
C4H6S			12	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	8
C5H8			25	25	1,3-Pentadiene, (E)-	1,4-Pentadiene	-1
C5H8			56	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	-8
C5H10			-4	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	1
C5H10			-53	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	-24