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/CEP-121G

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			-10	-7	allene	propyne	-3
C4H6			-75	-49	Cyclobutene	1,3-Butadiene	-26
C4H6			-55	-51	1,2-Butadiene	1,3-Butadiene	-3
C4H6			-1	3	1,2-Butadiene	1-Butyne	-4
C4H6			-123	-82	1-Methylcyclopropene	1,2-Butadiene	-41
C4H6			-27	-17	1,2-Butadiene	2-Butyne	-10
C4H6			70	42	Methylenecyclopropane	1-Methylcyclopropene	29
C3H6O			-109	-110	Oxetane	Propanal	1
C4H8			-37	-33	cyclobutane	1-Butene	-5
C3H4O2			78	29	2-Propenoic acid	β–Propiolactone	50
C4H6S			14	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	10
C5H8			28	25	1,3-Pentadiene, (E)-	1,4-Pentadiene	3
C5H8			70	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	6
C5H8			-54	-52	1,2-Butadiene, 3-methyl-	1,3-Butadiene, 2-methyl-	-2
C5H10			-6	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	-1
C5H10			-50	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	-21