The lack of concertedness in the general acid-base catalysis of the enolization of oxalacetic acid. A case for stepwise nucleophilic-general base catalysis

1976 ◽  
Vol 98 (3) ◽  
pp. 844-845 ◽  
Author(s):  
Paula Y. Bruice ◽  
Thomas C. Bruice
Keyword(s):  
Base Catalysis ◽  
Acid Base ◽  
Oxalacetic Acid ◽  
General Base ◽  
General Acid

Catalysis by the nucleolytic ribozymes

2011 ◽  
Vol 39 (2) ◽  
pp. 641-646 ◽  
Author(s):  
David M.J. Lilley
Keyword(s):  
Base Catalysis ◽  
Hairpin Ribozyme ◽  
Cleavage Reaction ◽  
Acid Base ◽  
Rate Enhancement ◽  
General Base ◽  
General Acid ◽  
Varkud Satellite Ribozyme

The nucleolytic ribozymes use general acid–base catalysis to contribute significantly to their rate enhancement. The VS (Varkud satellite) ribozyme uses a guanine and an adenine nucleobase as general base and acid respectively in the cleavage reaction. The hairpin ribozyme is probably closely similar, while the remaining nucleolytic ribozymes provide some interesting contrasts.

Deuterium exchange of C-methyl protons in lumazine derivatives

1970 ◽  
Vol 48 (2) ◽  
pp. 263-270 ◽  
Author(s):  
J. M. McAndless ◽  
Ross Stewart
Keyword(s):  
Proton Magnetic Resonance ◽  
Proton Magnetic Resonance Spectroscopy ◽  
Acid Catalysis ◽  
Deuterium Exchange ◽  
Base Catalysis ◽  
Resonance Spectroscopy ◽  
Methyl Group ◽  
General Base ◽  
General Acid ◽  
Acid Catalyzed

Proton magnetic resonance spectroscopy has been used to examine the deuterium exchange of the methyl protons in two lumazine derivatives. The exchange occurs at the C-7 methyl group in 6,7,8-trimethyllumazine (2) and at the C-6 methyl group in 1,7-dihydro-6,7,8-trimethyllumazine (3). The former reaction is subject to both general acid- and general base-catalysis but the latter only to general acid-catalysis. Plausible mechanisms for the reactions of both compounds are advanced, involving in the case of 3, acid-catalyzed addition of water across the C6—N5 double bond.

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