Matches in DBpedia 2016-04 for { <http://wikidata.dbpedia.org/resource/Q1092165> ?p ?o }
Showing triples 1 to 32 of
32
with 100 triples per page.
- Q1092165 subject Q8635670.
- Q1092165 subject Q8823548.
- Q1092165 abstract "SNi or Substitution Nucleophilic internal stands for a specific but not often encountered nucleophilic aliphatic substitution reaction mechanism. The name was introduced by Cowdrey et al. in 1937 to label nucleophilic reactions which occur with retention of configuration, but later was employed to describe various reactions that proceed with similar mechanism. A typical representative organic reaction displaying this mechanism is the chlorination of alcohols with thionyl chloride, or the decomposition of alkyl chloroformates, the main feature is retention of stereochemical configuration. Some examples for this reaction were reported by Edward S. Lewis and Charles E. Boozer in 1952. Mechanistic and kinetic studies were reported few years later by various researchers.Thionyl chloride first reacts with the alcohol to form an alkyl chloro sulfite, actually forming an intimate ion pair. The second step is the concerted loss of a sulfur dioxide molecule and its replacement by the chloride, which was attached to the sulphite group. The difference between SN1 and SNi is actually that the ion pair is not completely dissociated, and therefore no real carbocation is formed, which else would lead to a racemisation. This reaction type is linked to many forms of neighbouring group participation, for instance the reaction of the sulfur or nitrogen lone pair in sulfur mustard or nitrogen mustard to form the cationic intermediate.This reaction mechanism is supported by the observation that addition of pyridine to the reaction leads to inversion. The reasoning behind this finding is that pyridine reacts with the intermediate sulfite replacing chlorine. The dislodged chlorine has to resort to nucleophilic attack from the rear as in a regular nucleophilic substitution.In the complete picture for this reaction the sulfite reacts with a chlorine ion in a standard SN2 reaction with inversion of configuration. When the solvent is also a nucleophile such as dioxane two successive SN2 reactions take place and the stereochemistry is again retention. With standard SN1 reaction conditions the reaction outcome is retention via a competing SNi mechanism and not racemization and with pyridine added the result is again inversion.".
- Q1092165 thumbnail SNi_reaction_mechanism.gif?width=300.
- Q1092165 wikiPageWikiLink Q156.
- Q1092165 wikiPageWikiLink Q161532.
- Q1092165 wikiPageWikiLink Q2046985.
- Q1092165 wikiPageWikiLink Q210385.
- Q1092165 wikiPageWikiLink Q2134627.
- Q1092165 wikiPageWikiLink Q289532.
- Q1092165 wikiPageWikiLink Q36496.
- Q1092165 wikiPageWikiLink Q373406.
- Q1092165 wikiPageWikiLink Q409171.
- Q1092165 wikiPageWikiLink Q413363.
- Q1092165 wikiPageWikiLink Q414004.
- Q1092165 wikiPageWikiLink Q5282.
- Q1092165 wikiPageWikiLink Q586804.
- Q1092165 wikiPageWikiLink Q6057656.
- Q1092165 wikiPageWikiLink Q627.
- Q1092165 wikiPageWikiLink Q648191.
- Q1092165 wikiPageWikiLink Q658656.
- Q1092165 wikiPageWikiLink Q682.
- Q1092165 wikiPageWikiLink Q745930.
- Q1092165 wikiPageWikiLink Q804644.
- Q1092165 wikiPageWikiLink Q81166.
- Q1092165 wikiPageWikiLink Q838084.
- Q1092165 wikiPageWikiLink Q8635670.
- Q1092165 wikiPageWikiLink Q8823548.
- Q1092165 wikiPageWikiLink Q888529.
- Q1092165 comment "SNi or Substitution Nucleophilic internal stands for a specific but not often encountered nucleophilic aliphatic substitution reaction mechanism. The name was introduced by Cowdrey et al. in 1937 to label nucleophilic reactions which occur with retention of configuration, but later was employed to describe various reactions that proceed with similar mechanism.".
- Q1092165 label "SNi".
- Q1092165 depiction SNi_reaction_mechanism.gif.