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: wB97X-D/3-21G*

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			-0	-7	allene	propyne	7
C4H6			-47	-49	Cyclobutene	1,3-Butadiene	2
C4H6			-38	-51	1,2-Butadiene	1,3-Butadiene	13
C4H6			7	3	1,2-Butadiene	1-Butyne	4
C4H6			-15	-17	1,2-Butadiene	2-Butyne	2
C4H6			-109	-82	1-Methylcyclopropene	1,2-Butadiene	-27
C4H6			64	42	Methylenecyclopropane	1-Methylcyclopropene	22
C3H6O			-106	-110	Oxetane	Propanal	4
C4H8			-11	-33	cyclobutane	1-Butene	22
C3H4O2			21	29	2-Propenoic acid	β–Propiolactone	-8
C4H6S			-4	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	-8
C5H8			26	25	1,3-Pentadiene, (E)-	1,4-Pentadiene	1
C5H8			49	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	-15
C5H8			-38	-52	1,2-Butadiene, 3-methyl-	1,3-Butadiene, 2-methyl-	14
C5H10			-6	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	-0
C5H10			-34	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	-5