rapor 11 organik - ABSTRACT In this experiment, the purpose...

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ABSTRACT In this experiment, the purpose was to investigate E1 elimination mechanism with the reaction of cyclohexanol to cyclohexene. The reaction was acid catalyzed dehydration of alcohol and with catalyst sulfuric acid cyclohexene was obtained from cyclohexanol. And the product was obtained from the simple distillation and later it was reacted with bromine and potassium permanganate. The observations and results were all recorded. Simple distillation was used for distillation technique, and the distillate was seperated into test tubes, and to the one of them, bromine was added, and to the another potassium permanganate was added. Permanganate’s color changed from purple to brown, and bromium’s color changed brown to colorless, it became color solution which was light yellow. INTRODUCTION One of the most useful and general methods of preparing alkenes or olefins is based on the dehydration of alcohols with acids. Strong acids such as sulphuric and phosphoric acids are required to form the oxonium ion from which the hydronium ion is eliminated. “This cyclohexene from cyclohexanol reaction belongs to a broad class of organic transformations called elimination reactions, and within that class, this E1 elimination reaction constitutes another of the cornerstone reactions of organic chemistry. Mechanistically related to the S N 1 reaction, the E1 often competes with attempted substitution.” (5) Through proper choice of reaction conditions, it can usually be made the predominant or exclusive pathway. For example, one of the principal ways to prepare alkenes is via the acid catalyzed dehydration of an alcohol Dehydration of Alcohols - Zaitsev When an alcohol has two or three β carbons, dehydration is regioselective and follows the Zaitsev rule. The more substituted alkene is the major product when a mixture of constitutional isomers is possible. “2º and 3º alcohols react by an E1 mechanism (of the protonated alcohol) alcohols react by an E2 mechanism (of the protonated alcohol) The E1 Mechanisms The dehydrohalogenation of (CH 3 ) 3 CI with H 2 O to form (CH 3 )C=CH 2 can be used to illustrate the second general mechanism of elimination, the E1 mechanism.”(2) E1 mechanism It is a two-step process of elimination ionization and deprotonation .
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o Ionization , Carbon-halogen breaks to give a carbocation intermediate. o Deprotonation of the carbocation. Typical of tertiary and some secondary substituted alkyl halides. The reaction rate is influenced only by the alkyl halide. Reaction mostly present in absence of base or weak ones. (4) E1 eliminations happen with highly substituted alkyl halides due to 2 main reasons. Highly substituted alkyl halides are bulky, limiting the room for the E2 one-step
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rapor 11 organik - ABSTRACT In this experiment, the purpose...

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