Analysis Of Gaseous Products Lab Report

In this experiment, Analysis of Gaseous Products, a comparison between the elimination reactions created in the presence of an acidic and basic conditions was observed to be further analyzed through gas-liquid chromatography. These conditions were achieved by acid-catalyzed dehydration of a secondary and primary alcohol and based-induced dehydration of a secondary and primary bromide. As a result of these changing eliminations, gas-liquid chromatography makes it possible to separate and isolate volatile organic compounds to analyze the stereochemistry and regiochemistry of these compounds without decomposing them. Overall, gas-liquid chromatography of these compounds in acidic or basic conditions contributed in the identification and analysis

A strong nucleophile/base will likely force a second order reaction because the nucleophile/base is strong enough to attack the electrophilic carbon. In this case, KOtBu is a strong, bulky base and -Br is a good leaving group. Although the Potassium is not crucial to this reaction, the t-butoxide will proceed to attack the single beta hydrogen and knock off bromide to form an alkene, rearranging the bromobutane into an anti-periplanar position. In the KOtBu and 1-bromobutane reaction, there is one beta hydrogen present; this means there is only one possible product, 1-butene. However, there are two different types of beta hydrogens present in 2-bromobutane. This means there are two possible pathways for the t-butoxide can take, which can result in either cis or trans-butene products. In the 2-bromobutane reaction, t-butoxide will actually attack the beta hydrogen on the least substituted carbon group (methyl), resulting in the alkene, 1-butene (no cis- or trans-). Despite E2 mechanisms generally favoring Zaitsev products, when t-butoxide is involved, the Zaitsev’s rule is broken and the Hoffman product is favored because the bulkiness of t-butoxide forces it to attack the least substituted beta hydrogen. Following the discussed theories, it was

The acid-catalysed dehydration of a secondary and primary alcohol revealed that the E1 mechanism undergoes and favors rearrangement for a more stable carbocation; this reaction favors a Zaitsev product, which attacks the most substituted beta hydrogen. The base-induced dehydration of a secondary and primary bromide undergoes an E2 mechanism and favors a Hoffman product because of the presence of a sterically bulky base, which attacks the least substituted beta hydrogen. The percent compositions obtained through Gas Chromatography revealed that these favored types of products were present in the highest