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: PBE1PBE/6-31G*

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			11	-7	allene	propyne	17
C4H6			-28	-49	Cyclobutene	1,3-Butadiene	22
C4H6			-39	-51	1,2-Butadiene	1,3-Butadiene	12
C4H6			23	3	1,2-Butadiene	1-Butyne	20
C4H6			-10	-17	1,2-Butadiene	2-Butyne	7
C4H6			-64	-82	1-Methylcyclopropene	1,2-Butadiene	19
C4H6			46	42	Methylenecyclopropane	1-Methylcyclopropene	4
C3H6O			-99	-110	Oxetane	Propanal	11
C3H4O2			4	29	2-Propenoic acid	β–Propiolactone	-25
C4H6S			-0	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	-5
C5H8			38	25	1,3-Pentadiene, (E)-	1,4-Pentadiene	12
C5H8			57	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	-7
C5H8			-39	-52	1,2-Butadiene, 3-methyl-	1,3-Butadiene, 2-methyl-	13
C5H10			-13	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	-8
C5H10			-9	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	20