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(2df,p)

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			11	-7	allene	propyne	18
C4H6			-39	-51	1,2-Butadiene	1,3-Butadiene	13
C4H6			23	3	1,2-Butadiene	1-Butyne	20
C4H6			-7	-17	1,2-Butadiene	2-Butyne	9
C4H6			-57	-49	Cyclobutene	1,3-Butadiene	-7
C4H6			-84	-82	1-Methylcyclopropene	1,2-Butadiene	-2
C4H6			47	42	Methylenecyclopropane	1-Methylcyclopropene	5
C3H6O			-113	-110	Oxetane	Propanal	-3
C4H8			-30	-33	cyclobutane	1-Butene	2
C3H4O2			31	29	2-Propenoic acid	β–Propiolactone	2
C4H6S			0	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	-4
C5H8			57	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	-8
C5H8			-38	-52	1,2-Butadiene, 3-methyl-	1,3-Butadiene, 2-methyl-	13
C5H10			-12	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	-7
C5H10			-30	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	-1