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(2df,p)

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			17	-7	allene	propyne	23
C4H6			-19	-51	1,2-Butadiene	1,3-Butadiene	32
C4H6			31	3	1,2-Butadiene	1-Butyne	28
C4H6			-4	-17	1,2-Butadiene	2-Butyne	13
C4H6			-2	-49	Cyclobutene	1,3-Butadiene	47
C4H6			-59	-82	1-Methylcyclopropene	1,2-Butadiene	24
C4H6			49	42	Methylenecyclopropane	1-Methylcyclopropene	7
C4H6S			-5	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	-10
C5H8			43	25	1,3-Pentadiene, (E)-	1,4-Pentadiene	18
C5H8			53	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	-12
C5H10			-17	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	-12
C5H10			1	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	30