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: PBEPBE/6-31G(2df,p)

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			15	-7	allene	propyne	22
C4H6			29	3	1,2-Butadiene	1-Butyne	25
C4H6			-4	-17	1,2-Butadiene	2-Butyne	13
C4H6			-36	-51	1,2-Butadiene	1,3-Butadiene	15
C4H6			-38	-49	Cyclobutene	1,3-Butadiene	11
C4H6			-70	-82	1-Methylcyclopropene	1,2-Butadiene	12
C4H6			45	42	Methylenecyclopropane	1-Methylcyclopropene	4
C3H6O			-103	-110	Oxetane	Propanal	7
C4H8			-14	-33	cyclobutane	1-Butene	18
C3H4O2			13	29	2-Propenoic acid	β–Propiolactone	-15
C4H6S			-3	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	-7
C5H8			55	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	-9
C5H8			-36	-52	1,2-Butadiene, 3-methyl-	1,3-Butadiene, 2-methyl-	15
C5H10			-14	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	-9
C5H10			-15	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	14