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: CCSD/6-31G*

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			-5	-7	allene	propyne	2
C4H6			-76	-82	1-Methylcyclopropene	1,2-Butadiene	6
C4H6			-36	-49	Cyclobutene	1,3-Butadiene	13
C4H6			5	3	1,2-Butadiene	1-Butyne	2
C4H6			-37	-51	1,2-Butadiene	1,3-Butadiene	14
C4H6			46	42	Methylenecyclopropane	1-Methylcyclopropene	4
C3H6O			-114	-110	Oxetane	Propanal	-4
C4H8			-23	-33	cyclobutane	1-Butene	9