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: HF/aug-cc-pVDZ

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			-3	-7	allene	propyne	4
C4H6			-55	-51	1,2-Butadiene	1,3-Butadiene	-4
C4H6			4	3	1,2-Butadiene	1-Butyne	1
C4H6			-20	-17	1,2-Butadiene	2-Butyne	-3
C4H6			-65	-49	Cyclobutene	1,3-Butadiene	-16
C4H6			-89	-82	1-Methylcyclopropene	1,2-Butadiene	-7
C4H6			50	42	Methylenecyclopropane	1-Methylcyclopropene	9
C3H6O			-122	-110	Oxetane	Propanal	-12
C4H8			-38	-33	cyclobutane	1-Butene	-6
C3H4O2			54	29	2-Propenoic acid	β–Propiolactone	25
C4H6S			7	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	3
C5H8			26	25	1,3-Pentadiene, (E)-	1,4-Pentadiene	0
C5H8			68	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	4
C5H8			-53	-52	1,2-Butadiene, 3-methyl-	1,3-Butadiene, 2-methyl-	-2
C5H10			-5	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	1
C5H10			-37	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	-8