Syntheses, rate constants, and x-ray structures of alkylrhodoximes with .sigma.-donating alkyl groups methyl, ethyl isopropyl. A comparison with the analogous alkylcobaloximes, a vitamin B12 model

1990 ◽  
Vol 29 (18) ◽  
pp. 3437-3441 ◽  
Author(s):  
Nevenka Bresciani Pahor ◽  
Renata Dreos-Garlatti ◽  
Silvano Geremia ◽  
Lucio Randaccio ◽  
Giovanni Tauzher ◽  
...  
Keyword(s):  
Vitamin B12 ◽  
Rate Constants ◽  
Methyl Ethyl ◽  
X Ray ◽  
Alkyl Groups

Kinetics and Mechanism of Acid Catalyzed Decomposition of 1-Phenyl-3,3-dialkyltriazenes

1994 ◽  
Vol 59 (2) ◽  
pp. 401-411 ◽  
Author(s):  
Miroslav Ludwig ◽  
Pavla Valášková ◽  
Oldřich Pytela
Keyword(s):  
Rate Constants ◽  
Steric Effect ◽  
Aqueous Ethanol ◽  
Pivalic Acid ◽  
Decomposition Kinetics ◽  
Methyl Ethyl ◽  
Rate Determining Step ◽  
Alkyl Groups ◽  
Acid Catalyzed ◽  
Catalytic Rate

Five model 1-phenyl-3,3-dialkyltriazenes (methyl, ethyl, 2-propyl, butyl, cyclohexyl) have been synthesized and their acid-catalyzed decomposition kinetics have been investigated spectrophotometrically in aqueous ethanol (40 vol.%) with pivalic acid as the catalyst. The results show that the rate-determining step is catalyzed by the proton. The decrease in the observed rate constant at higher concentrations of pivalic acid is explained by the formation of an unreactive complex of the nondissociated acid and respective triazene. The steric effect of alkyl groups on the catalytic rate constants is discussed.

The decomposition of aliphatic N-nitro amines in aqueous sulfuric acid. Bisulfate as a nucleophile

1996 ◽  
Vol 74 (10) ◽  
pp. 1774-1778 ◽  
Author(s):  
Robin A. Cox
Keyword(s):  
Sulfuric Acid ◽  
Water Molecule ◽  
Rate Constants ◽  
Activation Parameters ◽  
Standard State ◽  
Aqueous Sulfuric Acid ◽  
Alkyl Groups ◽  
Different Temperatures ◽  
State Rate ◽  
Acid Catalyzed

In aqueous sulfuric acid, aliphatic N-nitro amines decompose to N2O and alcohols. An excess acidity analysis of the observed rate constants for the reaction shows that free carbocations are not formed. The reaction is an acid-catalyzed SN2 displacement from the protonated aci-nitro tautomer, the nucleophile being a water molecule at acidities below 82–85% H2SO4, and a bisulfate ion at higher acidities. Bisulfate is the poorer nucleophile by a factor of about 1000. Twelve compounds were studied, of which results obtained for nine at several different temperatures enabled calculation of activation parameters for both nucleophiles. The reaction appears to be mainly enthalpy controlled. The intercept standard-state rate constants are well correlated by the σ* values for the alkyl groups; the slopes are negative, with a more negative value for the slower bisulfate reaction. Interestingly the m≠m* slopes also correlate with σ*, although the scatter is bad. Key words: N-nitro amines, excess acidity, bisulfate, nucleophiles, acid-catalyzed, kinetics.

Tumor targeting vitamin B12 derivatives for x-ray activated chemotherapy (Conference Presentation)

2019 ◽  
Author(s):  
Jennifer R. Shell ◽  
Thomas Shell ◽  
Brian W. Pogue ◽  
Liberty Gendron ◽  
Colter G. Sheveland
Keyword(s):  
Vitamin B12 ◽  
Tumor Targeting ◽  
X Ray

Structure of Vitamin B12: X-ray Crystallographic Evidence on the Structure of Vitamin B12

Nature ◽  
1954 ◽  
Vol 174 (4443) ◽  
pp. 1169-1171 ◽  
Author(s):  
CLARA BRINK ◽  
DOROTHY CROWFOOT HODGKIN ◽  
JUNE LINDSEY ◽  
JENNY PICKWORTH ◽  
JOHN H. ROBERTSON ◽  
...  
Keyword(s):  
Vitamin B12 ◽  
X Ray

Synthesis, crystal structures and blue emission of zinc(II) halide complexes of 1-alkyl-imidazole and (–)-nicotine

2016 ◽  
Vol 71 (12) ◽  
pp. 1269-1277 ◽  
Author(s):  
Elnaz Hobbollahi ◽  
Barbora Veselkova ◽  
Manuela List ◽  
Günther Redhammer ◽  
Uwe Monkowius
Keyword(s):  
Mass Spectrometry ◽  
Blue Emission ◽  
Zinc Ion ◽  
Molecular Structures ◽  
Methyl Ethyl ◽  
X Ray Diffraction ◽  
X Ray ◽  
H Nmr ◽  
Tetrahedral Environment ◽  
Halide Complexes

AbstractZn(II) halide complexes of the form L2ZnX2 (X=Cl, Br, I) containing bio-relevant or bio-related ligands like 1-alkyl-imidazoles (alkyl=methyl, ethyl and iso-propyl) or (–)-nicotine are presented. All complexes were characterized by 1H NMR spectroscopy, mass spectrometry and elemental analysis. The molecular structures of the majority of complexes were determined by single crystal X-ray diffraction. The zinc ion exists in a tetrahedral environment coordinated by two halide anions and two nitrogen atoms of the N-heterocycles. Upon photoexcitation the nicotine complexes feature a blue emission which we tentatively assign to phosphorescence.

Unusual effect of bulky isopropyl group on robustness of the U-motif in pyrazolo[3,4-d]pyrimidine core based ‘Leonard linker’ compounds in comparison to methyl/ethyl group: A1H NMR and X-ray crystallographic study

2008 ◽  
Vol 888 (1-3) ◽  
pp. 327-336 ◽  
Author(s):  
Kamlakar Avasthi ◽  
Sangeeta Aswal ◽  
Sheikh M. Farooq ◽  
Resmi Raghunandan ◽  
Prakas R. Maulik
Keyword(s):  
Methyl Ethyl ◽  
Isopropyl Group ◽  
X Ray ◽  
Ethyl Group ◽  
Crystallographic Study ◽  
Unusual Effect

A Series of Imidazolyl-Containing Bisphosphonates with Abundant Hydrogen-Bonding Interactions: Syntheses, Structures, and Bone-Binding Affinity

2014 ◽  
Vol 67 (2) ◽  
pp. 192 ◽  
Author(s):  
Ling Qiu ◽  
Jianguo Lin ◽  
Liqing Wang ◽  
Wen Cheng ◽  
Yang Cao ◽  
...  
Keyword(s):  
High Performance ◽  
Binding Capacity ◽  
Imidazole Ring ◽  
Binding Affinities ◽  
Robust Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hydrogen Bonding Interactions ◽  
Alkyl Groups ◽  
Hydroxy Groups

A series of novel bisphosphonates (BPs) were designed and synthesised as longer-chain analogues of the clinically widely used BP–zoledronate (ZL). They were characterised by mass spectrometry, infrared spectroscopy, NMR spectroscopy, and single-crystal X-ray diffraction. All the crystals are zwitterions with one of the phosphonate oxygen atoms deprotonated and the hydrogen atom transferred to the nitrogen of the imidazole ring. A lot of strong hydrogen bonds are observed among the phosphonate oxygens, hydroxy groups, and protonated nitrogen atoms. An accurate, precise, and robust method was developed to determine the bone binding affinities of BPs based on high performance liquid chromatography. The results show that these five BPs have a strong affinity for hydroxyapatite and the binding capacity decreases when the substituted alkyl groups increase in size.

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