Time As A Determinate Of Final Product

In A Dehydration Reaction Essay, Research Paper

Time as a Determinate of Final Product in a Dehydration Chemical reaction

Robert Simack, Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, Alaska.

Abstraction: This survey involved acerb desiccation of 2-methylcyclohexanol. The consequences varied depending on the clip elapsed after initial reaction. I attempted to turn out the Evelyn Effect, which stated that over a period of clip the merchandises of the aforesaid reaction will beobserved to alter volume so that those merchandises formed by a cis isomer of 2-methylcyclohexanol will organize foremost. However, one time all molecules in the Commonwealth of Independent States isomer undergo reaction the staying trans configured 2-methylcyclohexanols will proliferate during the latter period of the reaction. I besides postulated as to the possible preparation of 1-ethylcyclopentene, and to the cause of such an event.

Introduction: After researching acid-catalyzed desiccation reactions ( McMurray ) and background on the Evelyn Effect ( Clausen ) I hypothesize that the cis isomer of 2-methylcyclohexanol will respond via an E1 type procedure organizing 1-methylcyclohexene harmonizing to anticipations from Zaitzev? s regulation ( Lehman ) .

This should be due to the fact that the Commonwealth of Independent States isomer has 2 anti-coplanar Hs. These two Hs should do the molecule more reactive. The trans isomer, with merely one anti-coplanar H, should be slower to respond and will organize a 3-methylcyclohexene. In add-on the 1-ethylcyclopentene will be formed from both the Commonwealth of Independent States and trans isomers but merely if the hydroxyl group is in an equatorial place. In that place negatrons from the ring may assail the intoxicant straight from behind forcing it off the ring and organizing a 5-membered ring alternatively.

Results & A ; Discussion: An NMR ( 300MHz ) spectra of the original reagent and the three fractions provided a immense sum of information in support of my hypothesis. Both Commonwealth of Independent States and trans isomers were present in the spectra for the original stuff every bit good as for the first two fractions. The intoxicant? s H showed up at about 3.79 and 3.1 for Commonwealth of Independent States and trans severally. In the spectra for pure get downing stuff ( ref: Jim Starr /Steve Standish NMR 24 March, 2000 ) Commonwealth of Independent States isomers of get downing stuff comprised merely 25 % of the sample compared to 75 % of trans as observed in the integrating of extremums. In the spectra for fraction one a 3:1 ratio of trans to cis was observed. In the spectra of fraction two the Commonwealth of Independent States isomer about disappeared ; the ratio was approximately 6:1 trans/cis. Finally, in the spectra of the 3rd fraction the Commonwealth of Independent States isomer was perfectly unperceivable while the integrating of trans was about twice that of the integrating from fraction one. These spectra show that Commonwealth of Independent States reacted first and was rapidly consumed by the reaction go forthing trans isomers to complete the reaction. Because it is kn

ain that the reaction with cis get downing stuff caused both 3-methylcyclohexene and 1-methylcyclohexene I postulated that the first merchandise of the latter phases of the reaction must be 3-methylcyclohexene, which is the exclusive merchandise of the trans reaction ( McMurray, fellow. 11.12 ) . In add-on to the Commonwealth of Independent States and trans peaks the extremum for both 3-methylcyclohexene and 1-methylcyclohexene could be found on the spectra at 5.7 and 5.4 severally. The NMR showed that the integrating of 1-methylcyclohexene dropped merely somewhat throughout the reaction while the integrating of 3-methylcyclohexene increased about tenfold. The findings from the spectra prove the hypothesis that the Commonwealth of Independent States reaction will travel the fastest followed by the trans because as the Commonwealth of Independent States is consumed it? s extremum at 3.79 will diminish every bit good as the extremum for 1-methylcyclohexene due to expiration of that merchandises formation.

Besides, extremums for 1-ethylcyclopentene Begin to demo in the spectra for the 2nd fraction and increase in size ( country beneath the extremum ) by the spectra of the 3rd fraction. At the root of this phenomena is steric hindrance. Both the Commonwealth of Independent States and trans isomers will organize 1-ethylcyclopentene ( fig. 1 ) . However, because of steric hindrance the trans isomer is favored to organize the 1-ethylcyclopentene. This fact will explicate why more of the pentene shows up in the 3rd fraction.

Finally, a bantam extremum showed at 4.6 in every fraction? s spectra bespeaking the presence of methylenecyclohexane. This merchandise formed from the original merchandise by acerb accelerator.

Experimental: An setup was constructed with a unit of ammunition underside flask topped by a claisen adapter in which was placed a thermometer and a condensation tubing. In the setup 150mmole of 2-methylcyclohexanol was assorted with 5mL H3PO4 and distilled. The distilled liquid was collected in three tubings, at about 4mL per tubing, labeled fraction 1, 2 and 3. Each fraction was placed in a extractor tubing and combined with 4mL concentrated NaHCO3. The aqueous bed was removed and MgSO4 was added for a concluding separation. The solid and aqueous beds were so removed and the concluding merchandise was combined with CDCL3 in an NMR tubing in readying for spectra. The liquid staying in the original setup was put through the separation procedure described above. However, alternatively of CDCL3 as a spectrum reagent we used CH2CL2. Besides, an NMR was non performed on the staying liquid but alternatively a GC.

Figure 1: Chemical reactions of Commonwealth of Independent States and trans isomers of 2-methylcyclohexanol during acid-catalyzed desiccation.

Bibliography

Clausen, Tom, ? Organic Chemistry 324 Lecture, ? Univeristy of Alaska, Fairbanks, March 20, 2000.

Lehman, John W. , Operational Organic Chemistry, 3rd ed. , New Jersey: Prentice-Hall, Inc. , 1999.

McMurry, John, Organic Chemistry, 4th ed. , California: Brooks/Cole Publication, 1996.