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: mPW1PW91/6-31G(2df,p)

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			9	-7	allene	propyne	16
C4H6			-33	-49	Cyclobutene	1,3-Butadiene	16
C4H6			-38	-51	1,2-Butadiene	1,3-Butadiene	14
C4H6			22	3	1,2-Butadiene	1-Butyne	19
C4H6			-10	-17	1,2-Butadiene	2-Butyne	7
C4H6			-67	-82	1-Methylcyclopropene	1,2-Butadiene	15
C4H6			46	42	Methylenecyclopropane	1-Methylcyclopropene	5
C3H6O			-100	-110	Oxetane	Propanal	10
C4H8			-10	-33	cyclobutane	1-Butene	23
C3H4O2			16	29	2-Propenoic acid	β–Propiolactone	-12
C4H6S			-1	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	-5
C5H8			56	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	-9
C5H8			-38	-52	1,2-Butadiene, 3-methyl-	1,3-Butadiene, 2-methyl-	14
C5H10			-13	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	-8
C5H10			-12	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	17