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: MP2=FULL/6-31G(2df,p)

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			-23	-7	allene	propyne	-16
C4H6			-57	-82	1-Methylcyclopropene	1,2-Butadiene	25
C4H6			40	42	Methylenecyclopropane	1-Methylcyclopropene	-1
C4H6			-30	-51	1,2-Butadiene	1,3-Butadiene	21
C4H6			-15	-49	Cyclobutene	1,3-Butadiene	35
C4H6			-13	3	1,2-Butadiene	1-Butyne	-16
C3H6O			-112	-110	Oxetane	Propanal	-2
C4H8			-5	-33	cyclobutane	1-Butene	28