elimination - Shulin Jiang TA: Jahnabi Roy 10/29/2011...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Shulin Jiang 10/29/2011 TA: Jahnabi Roy Section: AB1 Experiment 7. E1: Unimolecular Elimination Introduction To prepare alkenes, elimination is one of the most common ways. In this experiment the E1 process was carried out. The first step is protonating the alcohol under acid catalyst, producing an oxonium ion, a good leaving group. The RDS is dissociation of water to form a carbocation. Because E1 reaction is similar to SN1 reaction, both reactions will proceed through carbocation intermediate and compete with each other. To avoid alkene processing additional reaction to form the starting alchohol again, removing the product from the reaction mixture because the alkene always has a lower boiling point than alchohol. The product was tested for unsaturation using the Baeyer test. Potassium permanganate reacts with alkenes to form 1,2-diols and manganese dioxide, a brown solid. In this experiment cyclohexene was prepared via acid-catalyzed dehydration of cyclohexanol. The reaction was carried out and the rough product was collected by fractional distillation. A second simple distillation was needed to further purify the product. Both distillation processes were accessed by the boiling point range of products. Reaction Diagram: 1 Baeyer test: 1 Diagrams from CHEM 233 Organic Chemistry Laboratory Manual, page 43-44, UIUC, 2011
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Procedures Obtained 9ml cyclohexanol and transferred 7.5g into 25ml round-bottomed flask, then record the exact mass added. Added a magnetic stirring bar, transferred 2.0ml of 85% phosphoric acid and swirled gently. Assembled a fractional distillation apparatus with a column packed with steel wool, wrapped with aluminum foil. Collected all distillates between 75-85 in a 25ml flask cooled in ice bath. Stopped distillation when the reaction mixture became dark brown. Added some tips of anhydrous potassium carbonate and swirled over 10mins to dry. Purified the distillate via simple distillation, collected all distillates from 80-85 . Test the product with Bayer test: Placed 1 drop of product in 2ml 95% ethanol. Then added KMnO4 and swirled and counted drops before permanganate color persisted. Data and results Mass of the sample (g) Mass of the product (g) Ratio of yields (%) Fluctuated temperatur e ( ) Actual boiling point ( ) Theoretical boiling point ( ) 2 7.535 2.767 36.72 73.1 80.1-83.2 83.0-83.5 Baeyer test result: Positive after one drop. Discussion The expected results were not achieved in this experiment, but the concepts and techniques important to E1 unimolecular elimination reactions were completely understood. Unimolecular elimination reactions (E1) fall under the category of elimination which results in the formation of an alkene. This reaction results in the formation of a carbocation as an intermediate in order for the reaction to proceed. The
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/17/2011 for the course CHEM 233 taught by Professor Miller during the Spring '08 term at University of Illinois at Urbana–Champaign.

Page1 / 5

elimination - Shulin Jiang TA: Jahnabi Roy 10/29/2011...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online