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/6-31G*

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			1	-7	allene	propyne	8
C4H6			-62	-82	1-Methylcyclopropene	1,2-Butadiene	20
C4H6			-39	-51	1,2-Butadiene	1,3-Butadiene	12
C4H6			-38	-49	Cyclobutene	1,3-Butadiene	12
C4H6			13	3	1,2-Butadiene	1-Butyne	10
C4H6			42	42	Methylenecyclopropane	1-Methylcyclopropene	1
C3H6O			-103	-110	Oxetane	Propanal	7
C3H4O2			18	29	2-Propenoic acid	β–Propiolactone	-11
C4H6S			-0	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	-5
C5H8			32	25	1,3-Pentadiene, (E)-	1,4-Pentadiene	7
C5H8			52	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	-12
C5H8			-42	-52	1,2-Butadiene, 3-methyl-	1,3-Butadiene, 2-methyl-	10
C5H10			-9	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	-4
C5H10			-10	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	19