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: QCISD/6-31G*

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			-5	-7	allene	propyne	1
C4H6			46	42	Methylenecyclopropane	1-Methylcyclopropene	4
C4H6			-48	-49	Cyclobutene	1,3-Butadiene	1
C4H6			-48	-51	1,2-Butadiene	1,3-Butadiene	4
C4H6			4	3	1,2-Butadiene	1-Butyne	1
C4H6			-18	-17	1,2-Butadiene	2-Butyne	-1
C4H6			-77	-82	1-Methylcyclopropene	1,2-Butadiene	5
C3H6O			-116	-110	Oxetane	Propanal	-6
C4H8			-24	-33	cyclobutane	1-Butene	9
C5H8			27	25	1,3-Pentadiene, (E)-	1,4-Pentadiene	2
C5H8			61	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	-4