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/6-311+G(3df,2p)

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			-6	-7	allene	propyne	1
C4H6			-53	-51	1,2-Butadiene	1,3-Butadiene	-2
C4H6			-69	-49	Cyclobutene	1,3-Butadiene	-20
C4H6			-23	-17	1,2-Butadiene	2-Butyne	-6
C4H6			-89	-82	1-Methylcyclopropene	1,2-Butadiene	-7
C4H6			48	42	Methylenecyclopropane	1-Methylcyclopropene	7
C4H8			-43	-33	cyclobutane	1-Butene	-11
C3H4O2			52	29	2-Propenoic acid	β–Propiolactone	24
C4H6S			5	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	1
C5H8			26	25	1,3-Pentadiene, (E)-	1,4-Pentadiene	1
C5H8			67	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	3
C5H8			-51	-52	1,2-Butadiene, 3-methyl-	1,3-Butadiene, 2-methyl-	1
C5H10			-5	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	0
C5H10			-38	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	-9