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: LSDA/6-31G*

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C4H6			-20	-51	1,2-Butadiene	1,3-Butadiene	31
C4H6			-0	-49	Cyclobutene	1,3-Butadiene	49
C4H6			33	3	1,2-Butadiene	1-Butyne	30
C4H6			-4	-17	1,2-Butadiene	2-Butyne	13
C4H6			-58	-82	1-Methylcyclopropene	1,2-Butadiene	24
C4H6			47	42	Methylenecyclopropane	1-Methylcyclopropene	5
C4H6S			-4	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	-9
C5H8			44	25	1,3-Pentadiene, (E)-	1,4-Pentadiene	19
C5H8			54	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	-10
C5H10			-17	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	-12
C5H10			-0	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	29