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: QCISD/3-21G

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			-15	-7	allene	propyne	-8
C4H6			62	42	Methylenecyclopropane	1-Methylcyclopropene	20
C4H6			-77	-49	Cyclobutene	1,3-Butadiene	-28
C3H6O			-123	-110	Oxetane	Propanal	-13
C4H8			-41	-33	cyclobutane	1-Butene	-9
C4H6S			8	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	3
C5H10			-4	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	1
C5H10			-59	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	-30