Abstract:
:The kinetics of acetylation of alcohols by acetyl chloride and acetic anhydride, with N-methylimidazole as the catalyst, were studied in acetonitrile solution at 25 degrees; some measurements were also made with 4-dimethylaminopyridine as the catalyst. The acetic anhydride-N-methylimidazole system proceeds entirely by a general base catalysis, whereas the acetyl chloride-N-methylimidazole system reacts entirely via a nucleophilic route, with the intermediate formation of the N-acylated catalyst. The reaction of this intermediate with the alcohol is general base catalyzed. The acetyl chloride-4-dimethylaminopyridine system also reacts via the nucleophilic route. In the acetic anhydride-4-dimethylaminopyridine system a small fraction of the intermediate was detected. The acetic anhydride-N-methylimidazole system was studied in n-propanol-acetonitrile solvent mixtures; no spectral evidence for intermediate formation was seen. However, the hydrolysis reaction in acetic anhydride-N-methylimidazole, studied over a wide range of water-acetonitrile mixtures, revealed a change in mechanism from general base in dry acetonitrile to a solely nucleophilic route at high water concentrations.
journal_name
J Pharm Scijournal_title
Journal of pharmaceutical sciencesauthors
Pandit NK,Connors KAdoi
10.1002/jps.2600710503subject
Has Abstractpub_date
1982-05-01 00:00:00pages
485-91issue
5eissn
0022-3549issn
1520-6017pii
S0022-3549(15)44155-3journal_volume
71pub_type
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doi:10.1016/j.xphs.2018.04.002
更新日期:2018-08-01 00:00:00
abstract::Quality-by-design (QbD) is a systematic approach to drug development, which begins with predefined objectives, and uses science and risk management approaches to gain product and process understanding and ultimately process control. The concept of QbD can be extended to analytical methods. QbD mandates the definition ...
journal_title:Journal of pharmaceutical sciences
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doi:10.1002/jps.22325
更新日期:2011-03-01 00:00:00
abstract::Upon exposure to shaking stress, an IgG1 mAb formulation in both the liquid and lyophilized state formed subvisible particles. Because freeze-drying was expected to minimize protein physical instability under these conditions, the extent and nature of aggregate formation in the lyophilized preparation were examined us...
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更新日期:2015-02-01 00:00:00
abstract::The dependency of metformin in vivo disposition on the rate and extent of dissolution was studied. The analysis includes the use of fundamental principles of drug input, permeability, and intestinal transit time within the framework of a compartmental absorption transit model to predict key pharmacokinetic (PK) parame...
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abstract::A rapid and accurate method for the quantitative determination of the extent and ratio of amino and carboxyl group trimethylsilylation of 6-aminopenicillanic acid, 7-amino-3-methyl-delta3-cephem-4-carboxylic acid, and 7-amino-3-acetoxymethyl-delta3-cephem-4-carboxylic acid is presented. The method utilizes NMR spectro...
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doi:10.1002/jps.2600661230
更新日期:1977-12-01 00:00:00
abstract::Owing to proliferation of antibiotic-resistant bacteria, the use of antibiotics for livestock growth promotion is banned in many countries and alternatives to in-feed antibiotics are needed. Cinnamon essential oil exhibits strong in vitro antibacterial activity; however, direct addition of essential oils to animal fee...
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更新日期:2016-03-01 00:00:00
abstract::The molecular modeling program SYBYL was used to simulate the adsorption of various barbiturates by an activated charcoal surface. The compounds barbituric acid (BA), barbital (B), phenobarbital (PB), mephobarbital (M), and primidone (Pr) were modeled, and their structures were energetically minimized. These structure...
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abstract::Polyspecific organic cation transporters in the basolateral and brush border membrane of the kidney play a role in the elimination of many clinically important drugs and endogenous compounds. In this study we report the functional expression of organic cation transport activity in Xenopus laevis oocytes injected with ...
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abstract::Electrolytes often break emulsions to which they were added as active ingredients, adjuvants, or impurities. The stability of oil-in-water emulsions containing octoxynol 9 NF as the emulsifier and various added electrolytes was investigated by measuring droplet size, turbidity, and oil separation on storage at various...
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更新日期:1983-12-01 00:00:00
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abstract::The objective of the current study was to evaluate the performance of Raman and near-infrared (NIR) techniques combined with chemometrics in characterizing the critical quality attributes of brompheniramine (BP)-tannate complexes. Seven complexes were prepared and evaluated for chemical interactions, solubilities, dis...
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abstract::This study is to enhance the dissolution rate of a poorly water-soluble drug, quercetin, by fabricating nanocrystals using high-pressure homogenization. The particle size, crystallinity, dissolution, and antioxidant effects of fabricated quercetin nanocrystals have been investigated. Characterization of the original q...
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abstract::Drug stability studies are expensive and time consuming. Multiple batches are studied to ensure that a product will consistently remain within specifications for its entire expiration dating period. Some of these studies involve the same drug products in similar packages or in multiple strengths. Application of sound ...
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abstract::Levetiracetam therapy is often associated with high levels of individual variation in the recommended dose required to achieve preferential treatment. Thus, a reliable and dynamic regulation system to accurately tailor dose is necessary. The main objective of this study is to explore and prepare a dose-flexible contro...
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