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: B3LYP/CEP-31G

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			15	-7	allene	propyne	22
C4H6			-60	-51	1,2-Butadiene	1,3-Butadiene	-9
C4H6			26	3	1,2-Butadiene	1-Butyne	23
C4H6			7	-17	1,2-Butadiene	2-Butyne	24
C4H6			-59	-49	Cyclobutene	1,3-Butadiene	-10
C4H6			-99	-82	1-Methylcyclopropene	1,2-Butadiene	-17
C4H6			59	42	Methylenecyclopropane	1-Methylcyclopropene	17
C3H6O			-97	-110	Oxetane	Propanal	14
C4H8			-21	-33	cyclobutane	1-Butene	11
C3H4O2			39	29	2-Propenoic acid	β–Propiolactone	10
C4H6S			6	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	1
C5H8			39	25	1,3-Pentadiene, (E)-	1,4-Pentadiene	13
C5H8			76	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	12
C5H8			-59	-52	1,2-Butadiene, 3-methyl-	1,3-Butadiene, 2-methyl-	-7
C5H10			-9	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	-4
C5H10			-40	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	-11