1. Synthesize t-Butyl (or t-Pentyl) Chloride
Note: This experiment may utilize either t-Butyl Alcohol (m.p. 25.7oC) or t-Pentyl Alcohol (m.p. -9.5oC) as one of the starting reactants
Text References
Slayden - pp Pavia - Exp # pp Pavia - Tech pp

2. T-Butyl (t-Pentyl) Chloride Synthesis
Today’s Experiment
Reaction of t-Butyl Alcohol (or t-Pentyl Alcohol) with conc. HCL to form t-Butyl Chloride (or t-Pentyl Chloride)
Three-step Sn1 Nucleophilic Substitution Reaction
This is a First Order Rate Reaction where the Rate of Formation of t-Butyl Chloride (t-Pentyl Chloride) is dependent only on the concentration of the Alcohol, i.e., it is independent of the amount of acid (HCL) used
The strong acid (HCL) protonates the electron rich hydroxyl group (nucleophile) allowing it leave as a molecule of water
This leaves a highly electrophilic carbon atom (positvely charged carbocation) that can be attacked by the negatively charged chloride anion, forming the final product

3. T-Butyl (t-Pentyl) Chloride Synthesis
Today’s Experiment (Con’t)
NOTE: Rate of Formation and Limiting Reagent are independent of each other. Thus, the Limiting Reagent must be computed
Determine the limiting reagent and theoretical yield from the masses & moles of the two reactants (t-Butyl or t-Pentyl Alcohol & Conc HCl) and the stoichiometric molar ratios
This experiment will require the student to separate and wash (liquid/liquid Extraction) two immiscible liquids using a separatory funnel
Several steps of the experiment generate gases requiring care in using the separatory funnel and its stopcock

4. T-Butyl (t-Pentyl) Chloride Synthesis
t-Butyl Alcohol
(2-Methyl-2-Propanol)
B.P oC
M.P oC
Density g/mL
Refractive Index
Mol Wgt g/mole
Water Solubility - Soluble
t-Butyl Chloride
(2-Chloro-2-Methyl Propane)
( )
B.P oC
M.P oC
Density g/ml
Refractive Index
Mol Wgt g/mole
Water Solubility - Sl Soluble
Conc HCl
Molecular Wgt g/mole
Molarity moles/L
Density g/mL
% Acid

5. T-Butyl (t-Pentyl) Chloride Synthesis
t-Pentyl Alcohol
(2-Methyl-2-Butanol
B.P oC
M.P oC
Density g/mL
Refractive Index
Mol Wgt g/mole
Water Solubility - Soluble
t-Pentyl Chloride
(2-Chloro-2-Methyl Butane)
( )
B.P oC
M.P oC
Density g/ml
Refractive Index
Mol Wgt g/mole
Water Solubility - Slightly Sol
Conc HCl
Molecular Wgt g/mole
Molarity moles/L
Density g/mL
% Acid

6. T-Butyl (t-Pentyl) Chloride Synthesis
Stoichiometric Reaction
The Mechanism

7. T-Butyl (t-Pentyl) Chloride Synthesis
The Stoichiometric tert-Pentyl Reaction
The Mechanism

8. T-Butyl (t-Pentyl) Chloride Synthesis
Limiting Reagent Calculations
The yield (mass or moles) of the washed and dried t-Butyl (t-Pentyl) Chloride product is compared to the theoretical amount of product expected, which is computed from a “Limiting Reagent” calculation using the Stoichiometric Molar Ratio
The “Limiting Reagent” is that reactant whose mass (on a molar equivalent basis) is totally consumed in the reaction leaving an excess of the other reactant
The “Limiting Reagent”, thus, determines the maximum amount of product that can be expected
The results of the “Limiting Reagent computations” are presented in a table in the Data Report

9. T-Butyl (t-Pentyl) Chloride Synthesis
Limiting Reagent Calculations (Con’t)
Limiting Reagent Steps
Determine the mass of the alcohol to the nearest gram.
Measure the volume of conc HCL solution to be used to the nearest 0.1 mL
Compute the mass of the HCL from the volume, density, and % composition (see table)
From the amounts (mass) of reactants used, calculate the number of moles of each:
moles = mass / mol wgt
Moles of HCl can also be computed directly from the Volume and Molarity (12.0 moles/L).
If this approach is used, then back calculate the mass of HCL from the moles

10. T-Butyl (t-Pentyl) Chloride Synthesis
From the balanced reaction equation determine the molar ratio among the reactants and products i.e., how many moles of Alcohol react with how many moles of HCL to give how many moles of t-Butyl (t-Pentyl) Chloride. The ratio here is 1:1
If the ratio of moles of Alcohol to moles of HCl actually used is greater than the stoichiometric molar ratio, then the Alcohol is in “Excess” and HCl is “Limiting”
If, however, the ratio of actual moles of Alcohol to moles of HCl is less than the reaction molar ratio, then HCl is in excess and t-Butyl (t-Pentyl) Alcohol is “Limiting”

11. T-Butyl (t-Pentyl) Chloride Synthesis
Examples A + B  C Molar ratio A:B = 1 : 1 = 1.0 Moles actually used: A = 0.05; B = 0.12 Molar ratio A:B actually used: 0.05 / 0.12 = 0.42 The ratio of A:B is less than 1.00; thus A is limiting Only 0.05 moles of the 0.12 moles of B would be required to react with the 0.05 moles of A available Since 0.05 < 0.12; then B is in excess, A is limiting

12. T-Butyl (t-Pentyl) Chloride Synthesis
Examples (Con’t)
A B  C
Molar ratio A:B = 1 : 2 = 0.5
Moles actually used A = ; B =
Molar ratio A:B actually used = / = 0.30
The ratio A:B is less than 0.5, thus, A is limiting
Only  2 = moles of B are required to react with moles of A.
Since < 0.023:
B is in excess, A is limiting.
Any actual molar ratio less than the reaction molar ratio indicates “B” is in Excess and “A” is Limiting.
Any actual molar ratio greater than the reaction molar ratio indicates “A” is in Excess and “B” is Limiting

13. T-Butyl (t-Pentyl) Chloride Synthesis
Examples (Con’t)
In the Friedel-Crafts alkylation of Biphenyl with t-Butyl Chloride to form 4,4’-Di-tert-Butyl Biphenyl, g of Biphenyl is reacted with g of t-Butyl Chloride. The stoichiometric equation indicates that 2 moles of t-Butyl Chloride react with 1 mole of Biphenyl
Determine the “Limiting Reagent” and the “Theoretical Yield”
In the above example, “Biphenyl” is the limiting reagent because moles is less than / 2 = moles. Thus, a maximum of moles (1.838 g) 4,4’di- tert-Butyl Biphenyl can be expected
Amounts Actually Used Maximum Amounts Expected
1 Biphenyl t-Butyl Chloride  1 4,4’di-tert-Butylbiphenyl HCl
Mol Wgt
92.565
266.43
36.55
Mass (g)
1.064
2.129
1.838
0.504
Moles
0.0069
0.023
0.0138

14. T-Butyl (t-Pentyl) Chloride Synthesis
Theoretical Yield
The limiting reagent sets the maximum amount of product that can be expected
The actual number of moles of product is the product of the moles of Limiting reagent and the molar ratio of product to Limiting reagent
To get the mass of product simply multiply the expected moles of product by the molecular weight of the product

15. T-Butyl (t-Pentyl) Chloride Synthesis
Elements of the Experiment
Determining the masses of the reactants (2 procedures)
Alcohol mass is determined by weighing
HCl mass is determined by computing mass from volume, density and % Composition (HCl – 37.3 %)
Determining the moles of the reactants
Setting up the Stoichiometric equation
Determining the Limiting Reagent
Determining the Theoretical Yield
Mixing reagents and initiating the reaction

16. T-Butyl (t-Pentyl) Chloride Synthesis
Elements of the Experiment (Con’t)
Separate product from reaction mixture
Liquid/Liquid Extraction of product with H2O and NaHCO3 to Separate & Wash the product
Drying the product with Anhydrous Sodium Sulfate (Na2SO4)
Determining the Mass (Yield) of the Product
Computing the % yield
Determining the Refractive Index
Adjusting Refractive Index for temperature
Obtaining the Infrared Spectrum

17. T-Butyl (t-Pentyl) Chloride Synthesis
Macro Scale Procedure:
Obtain vial of t-Butyl (or t-Pentyl) Alcohol from instructor’s desk
Note: Melting point of t-Butyl Alcohol is near room temperature and could be solid if lab is cold. Warm vial with hands to melt
Weigh the vial and contents; record in pre-lab
Setup cork ring on iron ring to support funnel
Transfer sample to 125 ml Separatory Funnel using a long stem glass funnel
Reweigh the vial. In your report calculate the Mass of t- Butyl (or t-Pentyl) Alcohol
In your report compute the Moles of the Alcohol

18. T-Butyl (t-Pentyl) Chloride Synthesis
Macro Scale Procedure (Con’t):
Add 25 mL, measured to nearest 0.1 mL, of concentrated HCl to the separatory funnel
In your report calculate Mass of HCL
(vol(mL) * density(g/mL) * % comp (37.3))
In your report compute the moles of HCL Note: As an alternative, the Moles of HCl can be computed directly from the Volume and Molarity of Conc. HCl. (Back calculate to get mass)
In your report set up the Stoichiometric Equation, determine the Limiting Reagent, and calculate the Theoretical Yield

19. T-Butyl (t-Pentyl) Chloride Synthesis
Macro Scale Procedure (Con’t):
Stopper the funnel, firmly holding the stopper with your finger, and gently swirl the mixture for approximately one (1) minute
Invert the funnel and slowly open the stopcock to vent pressure
Close stopcock; swirl the mixture again; and again release the pressure
Repeat this process for 3-4 times until gas release is minimized
Two layers will form in the funnel
Note: Based on the densities of the organic layer and the aqueous layer (H20, HCl, etc.) determine which layer is on top

20. T-Butyl (t-Pentyl) Chloride Synthesis
Drain the aqueous reaction mixture into a large beaker
In the following steps the organic layer will be extracted once with Water, two (2) times with Sodium Bicarbonate (NaHCO3), and again with water
The Extraction procedure must be done in an expeditious manner as t-Butyl (t-Pentyl) Chloride is unstable in Water and Sodium Bicarbonate
Note: This can be one Procedure
Retain the organic fraction in the Separatory Funnel and the separated aqueous fraction in the waste beaker

21. T-Butyl (t-Pentyl) Chloride Synthesis
Wash (swirl and shake) the mixture with one 10 mL portion of Distilled Water
Hold the funnel stopper firmly in place with your thumb and gently shake to mix the contents
Carefully invert the funnel and release any excess pressure by slowly opening the stopcock
Close stopcock and repeat the mixing/venting process until gas is no longer being vented
Drain the aqueous phase into the waste beaker
Retain the organic phase (top layer) in the separatory funnel

22. T-Butyl (t-Pentyl) Chloride Synthesis
Add 10 mL of 5% aqueous Sodium Bicarbonate (NaHCO3) to the funnel containing the organic layer
Note: The Sodium Bicarbonate reacts with any aqueous acid (HCL) in the organic layer releasing Carbon Dioxide gas
Be careful when venting the gas!
Repeat the mixing and venting process several times until gas is no longer being vented
Allow the layers to separate; and drain the aqueous layer again into the waste Erlenmeyer flask
Repeat the washing process with a second 10 mL portion of 5% NaHCO3
Wash the organic layer again with 10 mL Distilled Water

23. T-Butyl (t-Pentyl) Chloride Synthesis
After removing the aqueous layer to the waste beaker, drain the organic layer into a small (50 mL), clean, dry beaker
With instructors help, add Anhydrous Sodium Sulfate to the crude product, swirling the mixture until it is clear Note: See p in Pavia for techniques on determining dryness of sample
Transfer the clear product into a clean, dry, pre-weighed 50 mL Erlenmeyer flask
Weigh the flask and contents
Determine the mass of product by difference
Calculate the percentage yield
Determine the Refractive Index; Correct for Temperature
Obtain IR Spectrum

24. T-Butyl (t-Pentyl) Chloride Synthesis
Semi-Micro Scale Procedure (Do not use this procedure unless specifically instructed to do so by Instructor)
Obtain vial of t-Butyl (t-Pentyl) Alcohol ( 4 mL) from instructor’s desk
Note: Melting point of t-Butyl Alcohol is near room temperature and could be solid if lab is cold. Warm vial with hands to melt
Weigh the vial and contents to nearest g; record in notebook
Transfer sample to Centrifuge Tube using a long stem glass funnel
Reweigh the empty vial
Calculate Mass of t-Butyl Alcohol
Calculate Moles of t-Butyl Alcohol

25. T-Butyl (t-Pentyl) Chloride Synthesis
Semi-Micro Scale Procedure (Con’t):
Add  8 mL, measured to nearest 0.1 mL, of concentrated HCl to the Centrifuge tube
In your report calculate Mass of HCL from the Volume, Density, % composition
Note: This calculation is different from Alcohol mass, therefore, it is a separate procedure
Compute Moles of HCl
Note: As an alternative, the Moles of HCl can be computed directly from the Volume and the Molarity of Conc. HCl
In the report, setup the Stoichiometric balanced equation
Determine the Limiting Reagent

26. T-Butyl (t-Pentyl) Chloride Synthesis
Semi-Micro Scale Procedure (Con’t):
Calculate the Theoretical Yield
Note: Each computation in the Limiting Reagent/ Theoretical Yield determination must be set up and all calculations shown
Screw the sealing cap onto the Centrifuge Tube and shake the tube gently for about 10 minutes. Be sure to unscrew the cap carefully every minute or so to vent any gases that may form
Two layers will form in the funnel Note: Based on the densities of the organic layer (t-Butyl Chloride) and the aqueous layer (H20, HCl, etc.) determine which layer is on top
Remove the Aqueous layer using a Pasteur Pipet
Place the aqueous waste in a waste beaker

27. T-Butyl (t-Pentyl) Chloride Synthesis
Semi-Micro Scale Procedure (Con’t):
The Extraction procedure that follows must be done in an expeditious manner as t-Butyl Chloride is unstable in Water and Sodium Bicarbonate
Extract (wash) the organic product, once with 10 mL Distilled Water, twice with 10 mL 5% Sodium Bicarbonate (NaHCO3) and once again with water
Be sure to vent gases carefully, especially with NaHCO Note: This is one Procedure
Each time, remove the Aqueous layer using a Pasteur Pipet
Place the aqueous waste in the waste beaker

28. T-Butyl (t-Pentyl) Chloride Synthesis
Semi-Micro Scale Procedure (Con’t):
Add Anhydrous Sodium Sulfate to the crude product, swirling the mixture until it is clear Note: See p in Pavia for techniques on determining dryness of sample
Decant the clear material into clean, dry, pre-weighed Erlenmeyer Flask
Weigh the flask and contents
Compute mass of product by difference
Compute the % yield
Determine the Refractive Index; Correct for Temperature
Obtain IR Spectrum

29. T-Butyl (t-Pentyl) Chloride Synthesis
The Report
The “Purpose” should reflect the type of reaction and principle reactants involved. It should also reflect introduction of any new techniques that you are to become familiar
The “Approach” is a sequential step by step overview of the principle procedures to be used, including calculations, such as mass, mole, limiting reagent, and theoretical yield determinations, as well as sample cleanup and reaction verification
It should also reflect how the results will be quantified, such as yield and percent yield
The “Procedures” should be stated in the student’s own words, using short, concise statements in “List” form

30. T-Butyl (t-Pentyl) Chloride Synthesis
The Report (Con’t)
In the “Summary” section summarize the “Results”, i.e. an overview in paragraph form of the experimental results obtained
In the “Conclusion” section consider the following questions:
What was the Molar ratio of HCl to t-Butyl Alcohol and what was the impact of this ratio on the selection of the Limiting Reagent and the amount of product expected?
What experimental results did you obtain to verify that the reaction produced the desired product?