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/3-21G*

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			-5	-7	allene	propyne	2
C4H6			-39	-51	1,2-Butadiene	1,3-Butadiene	13
C4H6			-22	-17	1,2-Butadiene	2-Butyne	-5
C4H6			-50	-49	Cyclobutene	1,3-Butadiene	-1
C4H6			-106	-82	1-Methylcyclopropene	1,2-Butadiene	-24
C4H6			63	42	Methylenecyclopropane	1-Methylcyclopropene	21
C3H6O			-98	-110	Oxetane	Propanal	12
C4H8			-21	-33	cyclobutane	1-Butene	12
C3H4O2			28	29	2-Propenoic acid	β–Propiolactone	-1
C4H6S			-3	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	-7
C5H8			26	25	1,3-Pentadiene, (E)-	1,4-Pentadiene	1
C5H8			46	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	-18
C5H8			-41	-52	1,2-Butadiene, 3-methyl-	1,3-Butadiene, 2-methyl-	10
C5H10			-6	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	-1
C5H10			-35	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	-6
C6H8			-2	-3	1,4-Cyclohexadiene	1,3-Cyclohexadiene	0