No comments The purpose of this experiment was to demonstrate the conversion of a primary alcohol, 1-butanol, to a primary bromoalkane, 1-bromobutane, a SN2 reaction. The conversion of 1-butanol to 1-bromobutane relies on sulfuric acid which plays two important roles. First, it protonates the alcohol of 1-butanol to form an oxonium ion which is a good leaving group.
SN2 and SN1 Reactions: Experiments 6 and 7 Preparation of 1-bromobutane from 1-butanol, 2-chloromethylbutane from 2-methylbutanol Introduction In the name SN1 or SN2, the S stands for substitution. One part of the starting molecule is replaced by something else.
The N stands for nucleophilic, which refers to a reaction where a nucleophile also referred to as Nu is attracted to the electrophile usually a carbon atom. The nucleophile attacks the electrophile to form a bond.
When the nucleophile attacks, it either forces the leaving group to break off in an SN2 reactionor it simply forms a bond to a carbocation which has already lost its leaving group in an SN1 reaction. Now it is clear to explain the meaning of the 1 or 2.
The 2 stands for bimolecular, because two components are involved simultaneously in a "concerted" reaction. Therefore, the leaving group is breaking off while the nucleophile is attaching, and so the result is that the nucleophile will be attached to the opposite side.
This is called an "inversion of configuration. The carbocation is very reactive, and the transition state involving the carbocation shows a trigonal planar stereochemistry. If in fact there is an equal energy of activation for the approach from either side, then SN1 will produce a racemic mixture after starting from a chiral compound.
Often, however, there are reasons why activation energy for approach from one side is greater, and so the product retains some unequal proportion of stereoisomers.
All the four parts involved in these reactions are important: To be a nucleophile, a molecule must have an unbonded pair of electrons.
To be a good nucleophile, generally, a molecule should be a strong base. A good leaving group will be a weak base, or form a strong conjugate acid. For an SN2 reaction, a good substrate will be preferably 1-degree and not beta-branched.
This is because, due to the mechanism of the reaction, it is affected by steric hindrances. It is also an acceptable mechanism under good conditions for 2-degree substrates. That is, the alpha carbon is bonded to two other carbons in the substrate.
For 3-degree substrates, this reaction is virtually not possible. To be a good solvent for SN2 reactions, the solvent should be polar aprotic. If the solvent, such as a protic solvent, solvates the nucleophile too greatly, it cages it in to interfere with its ability to attack the substrate.
The best solvent for SN1 reactions should be polar protic, to maximally stabilize the carbocation transition state and thereby lower the energy of activation. Table of reagents and reactants Table The product will be verified by gas chromatography by comparing the chromatograms of the starting material, 1-bromobutane standard, and your product.
Confirmation of your product, 1-bromobutane can also be performed by reacting the product with a solution of sodium iodide in acetone. THE PREPARATION OF 1-BROMOBUTANE FROM 1- BUTANOL Objective ; p-toluenesulfonyl chloride which will convert OH - into sulfonic acid ester to react with sodium bromide to produce 1-bromobutane.
Second, we react with the alcohol with phosphorus tribromide CONCLUSION. The. For preparation of 1-bromobutane: Discussion and conclusion. There are several significant things about the results of these two experiments.
Most importantly, we were successful in understanding the two types of reactions, and the differences between them. Essay on Discussion and Conclusion: Preparation of 1-Bromobutane. Conclusion: Preparation of 1-Bromobutane The purpose of this experiment was to demonstrate the conversion of a primary alcohol, 1-butanol, to a primary bromoalkane, 1-bromobutane, a SN2 reaction.
Synthesis of 1-bromobutane requires slow addition of the acid in order to protonate the alcohol to form a good leaving group, water, without having a high concentration of protonated alcohol to participate in an elimination reaction. Discussion and Conclusion: Preparation of 1-Bromobutane The purpose of this experiment was to demonstrate the conversion of a primary alcohol, 1-butanol, .