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: B1B95/CEP-31G

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			12	-7	allene	propyne	18
C4H6			4	-17	1,2-Butadiene	2-Butyne	21
C4H6			-55	-51	1,2-Butadiene	1,3-Butadiene	-4
C4H6			-33	-49	Cyclobutene	1,3-Butadiene	17
C4H6			-76	-82	1-Methylcyclopropene	1,2-Butadiene	6
C4H6			58	42	Methylenecyclopropane	1-Methylcyclopropene	16
C3H4O2			23	29	2-Propenoic acid	β–Propiolactone	-6
C4H6S			3	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	-1
C5H8			39	25	1,3-Pentadiene, (E)-	1,4-Pentadiene	14
C5H8			73	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	8
C5H8			-57	-52	1,2-Butadiene, 3-methyl-	1,3-Butadiene, 2-methyl-	-5
C5H10			-12	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	-7
C5H10			-15	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	14