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: B2PLYP/6-31G(2df,p)

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			-3	-7	allene	propyne	4
C4H6			9	3	1,2-Butadiene	1-Butyne	6
C4H6			-77	-82	1-Methylcyclopropene	1,2-Butadiene	5
C4H6			44	42	Methylenecyclopropane	1-Methylcyclopropene	2
C3H6O			-115	-110	Oxetane	Propanal	-5
C4H8			-25	-33	cyclobutane	1-Butene	7