Lab 7 SN2- Synthesis of 1-bromobutane
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University of Texas, San Antonio **We aren't endorsed by this school
Course
CHEM 1004
Subject
Chemistry
Date
Apr 22, 2024
Pages
5
Uploaded by kaymichael on coursehero.com
Kokeb Okbamichael
07/20/2020
Synthesis of Butyl Bromide from 1-Butanol by SN2 Reaction
Introduction
The purpose of this experiment is to perform a synthesis of butyl bromide from 1-butanol
by way of an SN2 reaction. An SN2 reaction mechanism includes the nucleophilic substitution of
originally a group of halides or any electron-withdrawing groups with a nucleophile within an organic compound. The stereochemistry found in an SN2 reaction is compared to that of a substrate, the nucleophile goes after the electrophilic center on the side that is opposite to the leaving group, changing the carbon atom. The kinetics found in the rate of an SN2 reaction is second order. The rate-determining step depends on the nucleophile concentration along with the
concentration of the substrate. In an SN2 reaction the nucleophile attacks from the "back", leading to steric hindrance. Primary alkyl halides have the least amount of steric hindrance compared to the other structures, so primary alkyl halides are preferred to undergo SN2 reaction mechanisms. In this lab, the reaction between butyl bromide and 1-butanol by utilizing sodium bromide and sulfuric acid, will be observed to understand the reaction taking place under SN2 mechanism. To isolate and observe the product, confirmatory tests will take place by way of distillation.
Reaction and Mechanism
Chemical Properties and Safety
Compound
Density
Boiling Point
Hazards
Sulfuric Acid
1.83 g/cm
3
337
℃
-
Corrosive
-
Causes irritation to eyes, skin, and
nose
-
Causes blindness
1-bromobutane
1.27 g/cm
3
102
℃
-
Cause irritation to eyes, nose, throat and respiratory tract
-
Cause headache and nausea
1-butanol
0.81 g/cm
3
117.7
℃
-
Cause eye, respiratory tract and skin irritation
Experimental Section
A sample of 11.1 grams of sodium bromide, 20 milliliters of 50% sulfuric acid, and 10 milliliters of 1-butanol is put into a 100 milliliter round bottom flask. A stir bar is placed inside the mixture and a condenser is hooked up for any reflux. The mixture is then heated to completely dissolve and brought to a light boil then the reflux is allowed to happen for 45 minutes. Two layers will appear with a clear and yellow separation. The reflux is then removed and 15 milliliters of water is set up to perform simple distillation. The product is then collected and the temperature should then read below 80
and 8-10 milliliters of product is collected. The
℃
product is transferred into a separatory funnel and 10 milliliters of 5% NaOH solution is added. Two layers will become apparent with butyl bromide being the bottom layer, this layer must then
be removed pouring the top liquid layer out. The pH of the bottom layer is checked to make sure the basicity is at a good level. The bottom layer is then drained into a clean beaker and a drying agent(anhydrous sodium sulfate) is then added into a clean beaker. The liquid is then transferred to a tarred vial and the product's weight is measured to determine the percent yield. The IR of the product to be derived and compared to the IR of 1-butanol. Confirmatory tests are then performed for silver nitrate and sodium iodide.
Data and Observations
Amount recovered is 6.104 grams which has been isolated and collected.
Calculations
Actual Yield = 6.104 g
Percent Yield:
Mass of n-butanol = (0.81 g/mL X 10 mL butanol) = 8.1 g n-butanol
# of moles of n-butanol = (8.1 g)/ (74.12 g/mol) = 0.1092 mol n-butanol
# of moles of NaBr = (11.1 g)/ (102.894 g/mol) = 0.1078 mol NaBr
Theoretical yield = 0.1078 mol X 137.03 g/mol(mass of 1-bromobutane) = 14.77 g of 1-
bromobutane
Percent Yield = (6.104 g/ 14.77 g) X 100% = 41.32 %
Discussions and Conclusions
The purpose of this experiment was to understand the synthesis of 1-bromobutane by observing the mechanism, SN2 reaction. By using the SN2 mechanism to track the synthesis of converting 1-butanol to butyl bromide, it brought forth the yield. During the synthesis of 1-
bromobutane, the nucleophile reacted with the backward direction of the reaction making the rate
of the reaction in the second order. From the data obtained, the IR graph showed an OH group at first at the peak and when the graph was run again for 1-bromobutane, the OH group disappeared
to show that the synthesis of SN2 was actually able to be successful. The percent yield is then calculated and turned out to be 41.32% showing that there was much lost in the performance of this experiment as shown in the video.
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