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(2df,p)

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			-6	-7	allene	propyne	1
C4H6			-75	-82	1-Methylcyclopropene	1,2-Butadiene	7
C4H6			46	42	Methylenecyclopropane	1-Methylcyclopropene	4
C4H8			-19	-33	cyclobutane	1-Butene	13