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: MP2/3-21G

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			-37	-7	allene	propyne	-30
C4H6			-44	-51	1,2-Butadiene	1,3-Butadiene	7
C4H6			-29	3	1,2-Butadiene	1-Butyne	-33
C4H6			-47	-17	1,2-Butadiene	2-Butyne	-30
C4H6			-72	-49	Cyclobutene	1,3-Butadiene	-22
C4H6			-117	-82	1-Methylcyclopropene	1,2-Butadiene	-35
C4H6			55	42	Methylenecyclopropane	1-Methylcyclopropene	13
C3H6O			-136	-110	Oxetane	Propanal	-25
C4H8			-38	-33	cyclobutane	1-Butene	-5
C3H4O2			39	29	2-Propenoic acid	β–Propiolactone	11
C4H6S			7	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	3
C5H8			17	25	1,3-Pentadiene, (E)-	1,4-Pentadiene	-8
C5H8			48	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	-16
C5H10			-5	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	0
C5H10			-52	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	-23