WK 14 Organic Chemistry Experiment Sn1 and Sn2 Reactions Lab Report

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The following is an example of an investigative lab report. Most of the experiments in Organic Chemistry I will follow this lab report format. Everything shown in bold below is what should actually be written in your report. Both your name and date should appear on separate lines on the right hand side of the page. Your Name Date Title of the Experiment Centered in the Page Experiment 2 Extraction and Evaporation. Separating the Components of “Panacetin” I. Introduction The introduction should be in your own words and explain the purpose behind the experiment. This will only require at most 10 sentences. The purpose can be found in the reading section from the departmental handout. II. Safety This section should have the NFPA rating for each chemical presented in the demonstration video. This will include the Health, Flammability, Reactivity, and other hazard ratings. You can find these ratings by doing an internet search of the chemical. III. Experimental Procedure While watching the demonstration video for the experiment, write the procedure stepwise, numbering your steps, in your own words. There should be enough detail such that anyone who reads your report could do the experiment without the use of a lab textbook. IV. Observations and Results This section will include things such as boiling range, melting point, color, time for reaction, spectra and etc. This section will include results related to your observations such as melting point and purity relationship, percent yield, percent recovery etc. V. Theory and Conclusions This section should indicate how your results related to the purpose of the experiment and what can be interpreted from your results. This section should indicate how your results prove the theory behind the reaction or procedure. Most of the information on the theory section can be found in your lecture book or in the prereading section of the lab experiment as well as the reading sections from the textbook, and research using the ACC library particularly AccessScience, KirkOthmer Encyclopedia of Chemical Technology, Van Nostrand’s Scientific Encylopedia, and Gale ebooks. This section will be graded the hardest and rambling results in grade deduction. You should be able to make your point in 3 to 5 pages. YOU MUST CITE YOUR SOURCES USING SUPERSCRIPTS TO INDICATE ANOTHER AUTHOR’S WORK. VI. Citations Any format is acceptable, I tend to use MLA. Tests of Substitution Mechanisms PURPOSE To test some aspects of nucleophilic substitution reaction mechanisms. LEARNING OBJECTIVES Students will learn to: • Identify the effects of substitution patterns on nucleophilic substitution reactions • Identify the effects of solvent on nucleophilic substitution reactions READING ASSIGNMENT There is no material to read in “Laboratory Techniques in Organic Chemistry” (4th ed.) by Mohrig, et al. You may wish to review your lecture materials related to nucleophilic substitution reactions of alkyl halides. BACKGROUND AND DISCUSSION Some of the substitution reactions discussed in the lecture this semester include nucleophile substitution of alkyl halides. Nucleophilic Substitution Nucleophilic substitution involves replacing a leaving group (typically a halogen) on an carbon atom with a nucleophile. sp3-hybridized R-X + Nuc- ____> R-Nuc + X- It has been well established that nucleophilic substitution occurs by two different mechanisms: SN1 and SN2. (1) SN2 Mechanism The SN2 mechanism is a concerted process where the nucleophile replaces the leaving group in a single step, with no reaction intermediate. Reactivity of the substrate goes as follows: methyl > 1o > 2o > 3o, where 3o substrates rarely react by SN2. This order is driven by transition state stability. In the transition state, there are 5 groups surrounding carbon, resulting in significant steric hindrance. With smaller groups, less crowding occurs, resulting in a faster reaction. (2) SN1 Mechanism The SN1 mechanism is a two-step process and involves a carbocation intermediate. Looking at the mechanism, you will see that the first step is rate-limiting. In this step a carbocation is formed. Its stability affects reaction rate. Carbocations are fundamentally electron deficient and alkyl groups inductively donate electron density, increasing their stability. The more stable the carbocation, the faster it forms, and the faster the rate of the reaction. As a result, reactivity of the substrates follows the pattern: 3o > 2o > 1o > methyl. (3) Effect of solvent Solvent plays and important role in nucleophilic reactions. To begin with, solvents can be polar or nonpolar. In nucleophilic substitution reactions, polar solvents are necessary because the nucleophile, leaving group, transition states and intermediates are all polar. Remember the rule “like dissolves like”. The next consideration is that polar solvents can be protic or aprotic. Protic solvents are those that undergo hydrogen bonding (e.g., H2O, ROH, NH3). Aprotic solvents do not undergo hydrogen bonding (e.g., CH2Cl2, CH3CN, acetone). Experiments suggest that polar protic solvents hinder the SN2 process, because they strongly solvate the nucleophile, inhibiting its ability to react. Polar aprotic solvents do not solvate the nucleophile as strongly, allowing it more freedom to react with the substrate. Reactions occurring by the SN1 mechanism are favorably affected by polar protic solvents. The transition state and intermediates are more polar than in SN2. Plus, it is likely that the solvent assists in carbocation formation, by pulling the leaving group away from carbon. In this experiment, you will study the effect of solvents on two different nucleophilic substitution reactions. In the first reaction, you will observe the reaction of alkyl bromides with silver nitrate dissolved in ethanol (EtOH). A balanced equation for the process is as follows: R-Br + EtOH + AgNO3 ____> R-OEt + AgBr ↓ The visual indicator is the formation of AgBr precipitate. The rate of precipitation is the indicator of how fast the reaction occurs. Note, ethanol serves as both the solvent and the nucleophile for this reaction. AgNO3 does not participate directly in the substitution part of the reaction. It is added because it is soluble in ethanol, but the product, AgBr, is not. In the second experiment, you will observe the reaction of alkyl bromides with sodium iodide dissolved in acetone. R-Br + NaI ____> R-I + NaBr ↓ The visual indicator here is the formation of NaBr precipitate. NaBr is insoluble in acetone, whereas NaI is soluble. Before you begin, fill out the prelab section of the report form, according to your instructor’s directions. SAFETY INFORMATION There are a variety of hazards associated with all of the chemicals used in these experiments. Dichloromethane and the alkyl bromides are toxic and are harmful if inhaled. Many are suspected carcinogens. Bromine is toxic and corrosive and produces dangerous vapors. Sodium iodide in acetone produces a lachrymator so avoid the fumes. EXPERIMENTAL PROCEDURE Perform all experiments in a well-ventilated area. A. Nucleophilic Substitution (1) Polar protic solvents Obtain 5 clean, dry test tubes and label with the following names: 1-bromobutane, 1chlorobutane, 2-bromobutane, 2-chlorobutane, and 2-chloro-2-methylpropane. Add 2 mL of a 0.1 M silver nitrate in ethanol solution to each test tube. Then add 1 drop of each alkyl halide to the appropriately labeled test tube, one after the other, as quickly as possible. Once all have been added, carefully shake the test tubes. You are looking for a precipitation reaction. Record the time required for appearance of the first sign of cloudiness. If, after 10 minutes, a relative order of reactivity cannot be established, put the test tubes in a warm water bath for up to 10 minutes. If after the time has elapsed, no reaction occurs, then record this result. (2) Polar aprotic solvents Obtain 5 clean, dry test tubes and label with the following names: 1-bromobutane, 2chlorobutane, 2-bromobutane, 2-chlorobutane and 2-chloro-2-methylpropane. Add 1 mL of a 15% sodium iodide in acetone solution to each test tube. Then, add 2 drops of each alkyl halide to the appropriately labeled test tube, one after the other, as quickly as possible. Once all have been added, carefully shake the test tube. Again, you are looking for a precipitation reaction. Record the time required for appearance of the first sign of cloudiness (discoloration without precipitate is not a sign of reaction). If an order of reactivity is not established after 10 minutes, place the test tubes in a warm water bath for up to an additional 10 minutes. After this time has passed, record the final results. OBSERVATIONS AND RESULTS Observations are in the table below and include if a precipitate formed and if elevated temperature was required. Complete the expected mechanism column as Sn1 or Sn2. Alkyl Halide Expected Mechanism NaI ppt formed Time to React 3 min No heat AgNO3 EtOH No rxn Time to React Expected Products if Reaction Occurs I Br O ppt formed Cl ppt formed Br No rxn Cl 5 min total 3 min at RT 2 min heat 7 min total 3 min at RT 4 min heat No rxn I O ppt formed 3 min I O ppt formed 4 min I O No rxn Cl ppt formed 10 sec I O THEORY AND CONCLUSIONS For the theory and conclusions section, give a short synopsis of Sn1 and Sn2. Also for any of the alkyl halides that reacted, write out a mechanism using arrow notation and any necessary transition states to show the reactions that took place. The nucleophiles as chosen in each case were weak nucleophiles and as such will only follow a substitution reaction if a reaction occurred.
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Please view explanation and answer below.Hi buddy! I'm sending an update regarding this task for now. The next message that I will send after this contains the final answer. Don't worry, I'll send it soonest. Thank you so much! 😍
View attached explanation and answer. Let me know if you have any questions.Hi buddy! Here is the file. It looks good for now, but I was hoping we could submit this first to align with the deadline and submit the final one via email just to be sure that the grade that will be given to this lab will be flying colors, to help with your grade lol. Will that be okay? Anyway, here is the file. Please take a look 😀 Thank you so much, buddy! 😍

Raheel Hussein
May 13, 2021

Experiment 11 Sn1 and Sn2 Reactions

I.

Introduction[7]
The purpose of this experiment is to test some aspects of nucleophilic

substitution reaction mechanisms. From there, the goal is to be able to identify the
effects of substitution patterns on nucleophilic substitution reactions as well as the
effects of solvent on nucleophilic substitution reactions. For this lab activity, would
need the review or refresh on the topic of nucleophile subsitution of alkyl halides.

II.

Safety
In this section, the essential information regarding the substances or mixtures

utilized in this experiment is generated from reference Material Safety Data Sheets
(see Citations). This is to ensure that proper handling in working with these
chemicals is observed.
1. 1-Bromobutane (C4H9Br)[1] and 2-Bromobutane (C4H9Br)[3]
NFPA Ratings:
Health Hazard – 2
Flammability

–3

Reactivity

–0

Other Hazards:

Combustible,

Inhalation

(Causes

respiratory

tract

irritation), Skin (When contacted, wash with soap and water), Eyes (Immediately
flush eyes with plenty of water), Ingestion (Do NOT induce vomiting unless directed
to do so by medical personnel)

2. 1-Chlorobutane (C4H9Cl)[2] and 2-Chlorobutane (C4H9Cl)[4]
NFPA Ratings:
Health Hazard – 2
Reactivity
Other Hazards:

Flammability – 3

–0
Combustible,

Inhalation

(Causes

respiratory tract irritation), Skin (When contacted, wash with soap and water), Eyes
(Immediately flush eyes with plenty of water), Ingestion (Do NOT induce vomiting
unless directed to do so by medical personnel), Wear personal protective equipment
3. 2-Chloro-2-methylpropane ((CH3)3CCl)[8]
NFPA Ratings:
Health Hazard – 2
Reactivity
Other Hazards:

Flammability – 3

–0
Combustible,

Inhalation

(Causes

respiratory

tract

irritation), Skin (When contacted, wash with soap and water), Eyes (Immediately
flush eyes with plenty of water), Ingestion (Do NOT induce vomiting unless directed
to do so by medical personnel), Wear personal protective equipment
4. Acetone (CH3)2CO[9]
NFPA Ratings:
Health Hazard – 1
Reactivity
Other Hazards:

Flammability – 3

–0
Combustible, Skin (When contacted, wash with soap and

water), Eyes (Immediately flush eyes with plenty of water), Ingestion (Very
hazardous when ingested and inhaled. Do NOT induce vomiting unless directed to
do so by medical personnel), Toxic to lungs, nervous system, and mucous
membranes when exposed for too long.

5. Silver Nitrate (AgNO3)[10]
NFPA Ratings:
Health Hazard – 3
Reactivity
Other Hazards:

–2

Flammability – 1
Specific – OX

Material contains oxidizing properties, Flammable,

Hazardous to Skin (When contacted, wash with soap and water), Eyes (Immediately
flush eyes with plenty of water), Ingestion (Very hazardous when ingested and
inhaled. Do NOT induce vomiting unless directed to do so by medical personnel)

III.

Experimental Procedure[5. 7]
1. The experiment should be performed in a well-ventilated area. The
experiment will focus on nucleophilic substitution of polar priotic and polar
apriotic solvents.
2. For polar priotic solvents, obtain 5 clean, dry test tubes. Label these with the
following names of compounds: 1-bromobutane, 1-chlorobutane, 2bromobutane, 2-chlorobutane, and 2-chloro-2-methylpropane.
3. Add 2 mL of a 0.1 M silver nitrate in ethanol solution to each test tube, then
add 1 drop of each alkyl halide to the correct test tube.
4. Next, shake the test tubes carefully. The goal is to gain a precipitation reaction.
5. Record the time required for the appearance of the first sign of cloudiness.
6. If, after 10 minutes, relative order of reactivity cannot be established, put the
test tubes in a warm water bath for up to 10 minutes.
7. Record the result even if the case is after the time has elapsed, no reaction
occurs.
8. Conduct the same process but this time, for polar apriotic solvents.
9. Add 1 mL of a 15% sodium iodide in acetone solution to each test tube.

10.Then, add 2 drops of each alkyl halide to the correct test tube. Shake the test
tube carefully. Observe and look for a precipitation reaction.
11.Record the time required for appearance of the first sign of cloudiness (the
reaction is not a discoloration without precipitate).
12.You can then place the test tubes in a warm water bath if an order of reactivity
is not established after 10 minutes. Longest time could be 20 minutes total.
After this time has passed, record the final results.
IV.

Observations and Results
The Table 1 below shows the observations, properties to be considered, if a

precipitation formation has been recorded, and if an elevated temperature was
required.
Table 1. Table of Observations, Mechanism, and Reactions[5, 7]
Alkyl
Halide

Expected
Mechanism

NaI

1o since the C is ppt
Br

bonded

to

to AgNO3
EtOH

3 min

No rxn

1 formed No heat

another

C,

therefore

it

should

Time
React

Time
React

to Expected
Products if
Reaction
Occurs
I

O

follow

Sn2.
1o since the C is ppt
bonded
Cl

to

1 formed 3 min at RT

another

C,

therefore

it

should
follow Sn2.

5 min total

also

No rxn
I

2 min heat
O

Carbon

Br

with ppt

halogen

7 min total

ppt

3 min

I

is formed 3 min at RT formed

bonded

to

2

4 mi...


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