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/6-31G

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			12	-7	allene	propyne	19
C4H6			25	3	1,2-Butadiene	1-Butyne	22
C4H6			-7	-17	1,2-Butadiene	2-Butyne	10
C4H6			-44	-51	1,2-Butadiene	1,3-Butadiene	7
C4H6			-75	-49	Cyclobutene	1,3-Butadiene	-26
C4H6			-112	-82	1-Methylcyclopropene	1,2-Butadiene	-30
C4H6			59	42	Methylenecyclopropane	1-Methylcyclopropene	17
C3H6O			-122	-110	Oxetane	Propanal	-12
C4H8			-40	-33	cyclobutane	1-Butene	-7
C3H4O2			55	29	2-Propenoic acid	β–Propiolactone	26
C4H6S			9	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	5
C5H8			39	25	1,3-Pentadiene, (E)-	1,4-Pentadiene	14
C5H8			63	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	-2
C5H8			-43	-52	1,2-Butadiene, 3-methyl-	1,3-Butadiene, 2-methyl-	8
C5H10			-12	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	-7
C5H10			-46	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	-17