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: B3LYPultrafine/6-31+G**

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			13	-7	allene	propyne	19
C4H6			49	42	Methylenecyclopropane	1-Methylcyclopropene	7
C3H6O			-114	-110	Oxetane	Propanal	-4
C4H8			-34	-33	cyclobutane	1-Butene	-2
C4H6S			-0	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	-4
C5H8			-43	-52	1,2-Butadiene, 3-methyl-	1,3-Butadiene, 2-methyl-	9