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			15	-7	allene	propyne	21
C4H6			5	-17	1,2-Butadiene	2-Butyne	22
C4H6			-52	-51	1,2-Butadiene	1,3-Butadiene	-1
C4H6			-13	-49	Cyclobutene	1,3-Butadiene	36
C4H6			-47	-82	1-Methylcyclopropene	1,2-Butadiene	36
C4H6			44	42	Methylenecyclopropane	1-Methylcyclopropene	3
C3H4O2			-13	29	2-Propenoic acid	β–Propiolactone	-41
C4H6S			-6	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	-10
C5H8			38	25	1,3-Pentadiene, (E)-	1,4-Pentadiene	13
C5H8			68	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	4
C5H8			-53	-52	1,2-Butadiene, 3-methyl-	1,3-Butadiene, 2-methyl-	-1
C5H10			-11	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	-6
C5H10			2	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	31