Lab+2+-+Solvent+Effects+in+SN1

 Solvent Effects in SN1 __**﻿**__ __ Introduction __

In organic chemistry, a large majority of the reactions chemists see occur between a nucleophile and an electrophile. One of the reactions studied is a substitution reaction. A substitution reaction can happen in one of two ways. It can be carried out via SN1 or SN2 reaction. The difference between the two are how many steps it takes during the reaction for the products to be produced. In an SN1 nucleophilic substitution reaction an important factor to consider is the solvent. In this experiment the reaction between the solvent 1-propanol or acetone and an alkyl halide were studied. Special attention was paid to the rate of the reaction between the solvent and reagents and were measured by monitoring the production of acid throughout the experiment. The acidity was tested by way of an acid-base indicator being added to the mixture. When enough acid is generated in reaction, the color of the indicator will change, in this lab’s case, from a blue-green to yellow. Measuring the time for this color change to happen allows for an estimated rate of the SN1 reaction.

When you dive into writing one of these introductions, you may assume your audience has some knowledge of chemistry. Imagine they are your peers, but at a different institution, perhaps. While you should emphasize the relevant concepts that are under investigation you do NOT need to explain more general concepts (like what a substitution reaction is).

Also: show the reaction right at the beginning of the report! It will clarify much for your reader.

Here is what I have fixed for the introduction! If there is something you guys don't like let me know :) Shoot me a text. I'm heading to Prineville so wont have my computer handy for a while!!! I LOVE YOU GUYS!

__ Procedure __

 The specific procedure was given as a physical handout:  please give me a citation here.


 * Part 1




 * Table of Reagents




 * Part 2




 * Addendum: Isopropanol was not actually used; the alcohol used for a reagent was 1-propanol instead.  I'm glad you noticed this! and I apologize for the confusion.

 The chemicals used in this lab:


 * Name: 1-propanol
 * IUPAC Name: Propan-1-ol
 * <span style="font-family: Verdana,Geneva,sans-serif;">CAS #: 71-23-8
 * <span style="font-family: Verdana,Geneva,sans-serif;">Compound Formula: C3H8O
 * <span style="font-family: Verdana,Geneva,sans-serif;">Structure:
 * <span style="font-family: Verdana,Geneva,sans-serif;">[[image:MSP110419e4bi83i5egh7c90000518cbb0a55765e6g.gif width="175" height="41"]]


 * <span style="font-family: Verdana,Geneva,sans-serif;">Name: 2-chloro-2-methylpropane
 * <span style="font-family: Verdana,Geneva,sans-serif;">IUPAC Name: 2-chloro-2-methylpropane
 * <span style="font-family: Verdana,Geneva,sans-serif;">CAS #: 507-20-0
 * <span style="font-family: Verdana,Geneva,sans-serif;">Compound Formula: C4H9Cl
 * <span style="font-family: Verdana,Geneva,sans-serif;">Structure:
 * <span style="font-family: Verdana,Geneva,sans-serif;">[[image:MSP318219e4bb6a732c1ba1000018gc79f6iea40b04.gif width="113" height="81"]]


 * <span style="font-family: Verdana,Geneva,sans-serif;">Name: Bromothymol (blue)
 * <span style="font-family: Verdana,Geneva,sans-serif;">IUPAC Name: sodium 2-[(Z)-(3-bromo-4-hydroxy-2-methyl-5-propan-2-yl-phenyl)-(3-bromo-2-methyl-4-oxo-5-propan-2-yl-1-cyclohexa-2,5-dienylidene)methyl]benzenesulfonate
 * <span style="font-family: Verdana,Geneva,sans-serif;">CAS#: 34722-90-2
 * <span style="font-family: Verdana,Geneva,sans-serif;">Compound Formula: C27H27Br2NaO5S
 * <span style="font-family: Verdana,Geneva,sans-serif;">Structure:
 * <span style="font-family: Verdana,Geneva,sans-serif;">[[image:MSP400519e4badb80a2befc000025d4e20gihh4f1ie.gif]]


 * <span style="font-family: Verdana,Geneva,sans-serif;">Name: Sodium Hydroxide
 * <span style="font-family: Verdana,Geneva,sans-serif;">IUPAC Name: Sodium Hydroxide
 * <span style="font-family: Verdana,Geneva,sans-serif;">CAS#: 1310-73-2
 * <span style="font-family: Verdana,Geneva,sans-serif;">Compound Formula: HNaO
 * <span style="font-family: Verdana,Geneva,sans-serif;">Structure:
 * <span style="font-family: Verdana,Geneva,sans-serif;">[[image:MSP424919e4bb1d918i390g000040fg7f91de9ee7e4.gif width="112" height="45"]]


 * <span style="font-family: Verdana,Geneva,sans-serif;">Name: Hydrochloric Acid
 * <span style="font-family: Verdana,Geneva,sans-serif;">IUPAC Name: Hydrogen Chloride
 * <span style="font-family: Verdana,Geneva,sans-serif;">CAS#: 7647-1-0
 * <span style="font-family: Verdana,Geneva,sans-serif;">Compound Formula: ClH
 * <span style="font-family: Verdana,Geneva,sans-serif;">Structure:
 * <span style="font-family: Verdana,Geneva,sans-serif;">[[image:MSP513819e4be3e3731ehc100003680b583cb0ecc8e.gif width="81" height="26"]]

__ Data __


 * <span style="font-family: Verdana,Geneva,sans-serif;">Observations
 * <span style="font-family: Verdana,Geneva,sans-serif;">In all flasks, mixture started out blue and smoothly transformed to a pale yellow, at varying rates listed in the tables below.





grouping the acetone data together, and the 1-propanol data together, would make any trends easier to see (or would make it easier to recognize if there is NO trend between the two groups).

__ Analysis __

<span style="font-family: Verdana,Geneva,sans-serif;">The more water present in the system (a **polar protic** solvent itself) correlated with reduced reaction times as all of the reagents remained constant. <span style="color: #800000; font-family: Verdana,Geneva,sans-serif;">true! Any other trends, or an absence of a trend where you might expect it?





__ Discussion/ ____ ﻿Conclusion __ <span style="font-family: Verdana,Geneva,sans-serif;"> From the tables above, one can see that when water dominated the mixture the reaction process was noticeably faster. However, there are a few things to consider when looking at the results. Precision was a large factor in the procedure and while the measurements of the reagents and solvents were measured out as accurately as possible there was still a large amount of room for potential error. The timing of reaction progress was done through use of stopwatches, and possible error could result from inaccuracies and variability in timing methods. It would have also been beneficial to utilize more data points throughout the entire class, which would give a wider range of specifics and could possibly help identify trends at a quicker pace. These are all good points.

<span style="font-family: Verdana,Geneva,sans-serif;">After the nucleophilic substitution reaction was complete it became apparent that the amount of water in the system effected <span style="color: #800000; font-family: Verdana,Geneva,sans-serif;"> (**a**ffected) <span style="font-family: Verdana,Geneva,sans-serif;"> the time it took for the reaction to take place. Water being a polar protic solvent is what enabled it to have an affect on the rate at which the reaction was completed. The more polar protic solvent in the system the faster an S <span style="font-family: Verdana,Geneva,sans-serif; font-size: 80%; vertical-align: sub;">N <span style="font-family: Verdana,Geneva,sans-serif;">1 reaction will be carried out. Protic solvents involve H-Bonding which will push the S <span style="font-family: Verdana,Geneva,sans-serif; font-size: 80%; vertical-align: sub;">N <span style="font-family: Verdana,Geneva,sans-serif;">1 because the formation of the carbocation is the rate-determining step and thus, water, for this procedure was the best solvent for the procedure to take place as it stabilizes ions in the mixture such as the carbocation intermediate.

<span style="color: #800000; font-family: Verdana,Geneva,sans-serif;">This certainly explains the acetone/water data. But what about the solvent that was alcohol in water? In that case, 100% of your solvent molecules are protic. There are some interesting nuances in this data that you don't appear to have grappled with.


 * <span style="font-family: Verdana,Geneva,sans-serif;">Post Lab Question #1: Suggest 3 other solvents that might be effective for completing the Sn1 reaction we performed. **

<span style="font-family: Verdana,Geneva,sans-serif;"> There are many potential solvents that would complete the reaction that was performed in lab however, all must be polar protic in order to expedite the S <span style="font-family: Verdana,Geneva,sans-serif; font-size: 80%; vertical-align: sub;">N <span style="font-family: Verdana,Geneva,sans-serif;">1 reaction. A few good polar protic solvents are:


 * Ammonia (NH₃)
 * Acetic Acid (C₂H₄O₂) or (AcOH)
 * Methanol (CH₄O)
 * Ethanol (C₂H₆O)


 * <span style="font-family: Verdana,Geneva,sans-serif;">Post Lab Question #2: Suggest a different alkyl halide that might be used if we wanted to get evidence (from polarimetery) that our reaction actually proceeds by Sn1 rather than Sn2. **

<span style="font-family: Verdana,Geneva,sans-serif;">A good alkyl hallide that will turn the mixture racemic (50/50 chance of there being an (S) or (R) configuration) is 2-bromo-3-ethyl-1-methylpropane. <span style="color: #800000; font-family: Verdana,Geneva,sans-serif;"> Oh, crud. I think you have the right idea, but this name is not correct. It is chiral in nature and therefore a polarimetry test would tell us the degrees rotated during the reaction process. Regardless of starting out with an (R) or an (S), S <span style="font-family: Verdana,Geneva,sans-serif; font-size: 80%; vertical-align: sub;">N <span style="font-family: Verdana,Geneva,sans-serif;">1 reactions tend to proceed when the carbon atom is surrounded by large bulky groups. These large groups prevent S <span style="font-family: Verdana,Geneva,sans-serif; font-size: 80%; vertical-align: sub;">N <span style="font-family: Verdana,Geneva,sans-serif;">2 reactions from happening and sterically hinder the nucleophile from coming in and attaching to the electrophile. Therefore since S <span style="font-family: Verdana,Geneva,sans-serif; font-size: 80%; vertical-align: sub;">N <span style="font-family: Verdana,Geneva,sans-serif;">1 is allowed to proceed the nucleophile can choose to attack the electrophile from either side, once again, leading to a racemic mixture.

<span style="color: #800000; font-family: Verdana,Geneva,sans-serif;">This report earned the following scores for: format (2/2) style (1.5/2) data (2.5/3) quality of result (1/1) quality of reported data (1/1) conclusion (1/2) error (1/1) post-lab Q (1.5/2) for a total of 11.5/14. A lot of the basics here are really good....there is still also some room for improvement.

__<span style="font-family: Verdana,Geneva,sans-serif; font-size: 20px;">Notes __

The chemical structures, formulas, and vital statistics of each compound was researched using [|Wolfram Alpha computational knowledge engine] and confirmed using the [|CRC Handbook of Chemistry and Physics [90th Edition.]]