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: M06-2X/aug-cc-pVTZ

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			-0	-7	allene	propyne	6
C4H6			-69	-82	1-Methylcyclopropene	1,2-Butadiene	14
C4H6			45	42	Methylenecyclopropane	1-Methylcyclopropene	3
C4H6			-28	-51	1,2-Butadiene	1,3-Butadiene	23
C4H6			-36	-49	Cyclobutene	1,3-Butadiene	13
C4H6			10	3	1,2-Butadiene	1-Butyne	7
C3H6O			-104	-110	Oxetane	Propanal	6
C4H8			-27	-33	cyclobutane	1-Butene	5