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: PBEPBE/cc-pV(T+d)Z

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			14	-7	allene	propyne	21
C4H6			-75	-82	1-Methylcyclopropene	1,2-Butadiene	7
C4H6			-47	-49	Cyclobutene	1,3-Butadiene	2
C4H6			-39	-51	1,2-Butadiene	1,3-Butadiene	13
C4H6			-5	-17	1,2-Butadiene	2-Butyne	12
C4H6			47	42	Methylenecyclopropane	1-Methylcyclopropene	5
C3H4O2			26	29	2-Propenoic acid	β–Propiolactone	-3
C5H8			38	25	1,3-Pentadiene, (E)-	1,4-Pentadiene	13
C5H8			57	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	-7
C5H8			-39	-52	1,2-Butadiene, 3-methyl-	1,3-Butadiene, 2-methyl-	13
C5H10			-13	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	-8
C5H10			-20	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	9