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/6-31+G**

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			17	-7	allene	propyne	24
C4H6			29	3	1,2-Butadiene	1-Butyne	26
C4H6			-2	-17	1,2-Butadiene	2-Butyne	15
C4H6			-40	-51	1,2-Butadiene	1,3-Butadiene	11
C4H6			-43	-49	Cyclobutene	1,3-Butadiene	6
C4H6			-73	-82	1-Methylcyclopropene	1,2-Butadiene	9
C4H6			47	42	Methylenecyclopropane	1-Methylcyclopropene	6
C3H6O			-107	-110	Oxetane	Propanal	4
C4H8			-19	-33	cyclobutane	1-Butene	14
C3H4O2			24	29	2-Propenoic acid	β–Propiolactone	-5
C4H6S			-4	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	-8
C5H8			38	25	1,3-Pentadiene, (E)-	1,4-Pentadiene	13
C5H8			58	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	-6
C5H8			-40	-52	1,2-Butadiene, 3-methyl-	1,3-Butadiene, 2-methyl-	12
C5H10			-12	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	-7
C5H10			-17	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	12