Question

E2 reaction of 2-bromoheptane

Lab Report Form: E2 Reaction of 2-Bromoheptane Before Lab Complete the first two columns of the Results table below, drawing the alkene products in order of increasing boiling point (lowest boiling point at top of table). Provide structures and names in the first column. Results Perform calculations for the relative percentages of the three alkenes on the copy of your GC graph, clearly and neatly showing your work. Area is from the GC trace. Percentages should add up to 100 % for the results for a given base. Elimination Product Boiling Ret. time (name and structure) point (eC) (min) NaOMe KO'Bu Area Area Percent Percent 1-heptenc प t 235 93.6 3.49 15044 I0398 20 3'/. transheptaenc 2 35 to 235 10D 32345 98.0 3-78 32745 2359 53.37 ৭৪ xI00 ৯১৩ Cis-hept-2-ene 31.78 e 235 v100 98.5 4.05 3478 9339 21/A ३।2 235

Answer 1

The heptane molecule & 2- Bromcheptanie as can be written as: Braho M as the reaction proceeds E2, so, the mechanism has only single step and is concerted, general can be shown: By Cat 4", - CuHg + H Base +88 C Base The transition state is E2 is lower in energy as compared to El, so easily attainable. Į E2 1 E1 t → Regiochemistry The elimination can produce both 1- Heptene & 2- Heptene, Suthy E, A M ilano trans. alkene having more stability will be formed in greater ratio. the order of stability trans-2 Heptene> cist Hepteret Heptene

us as we have two different bases in two different experime Naome ie Na Ochy and KöBu se kocin here by structure, kotBu is bare with larger (size) as compared to NaOCHy , so, kotBu will be sterically hindered and it would easier to abstract the proton from C1 Carbon of Z-Bromo heptane, while it will be sterically easier for Nadchy to abstract from ca. So, with larger base, we get to Heptene as major product & with smaller base, we get 2-Heptene Now, as out of trans & cis isomers of Hept-2-ene, the trans-isomer is more stable because of less steriac hinderance so it formed in more proportion, see the models. It KötBu Na OCH

conclusion Wwith KotBu result – (2) with NaOct result Hept-t-ere trans Hept-2-ene