Preparation of 2-chloro-2-methylbutane

 

            The reaction is SN1. The overall reaction is:

 

                        CH3                                                                                  CH3

            CH3 C CH2OH           +          HCl     «                       CH3 C CH2Cl

                        CH3                                                                                  CH3

 

WEAR GLOVES

  

Procedure

 

    Take your 125 mL separatory funnel and 100 mL graduated cylinder to hood #1.

    Place 10mL. of 2-methyl-2-butanol and 25mL of concentrated (12M) HCl.

 

    Swirl the contents of the separatory funnel gently, without the stopper in the funnel.

 

    After swirling for about 1 minute, stopper and invert the funnel.

 

    After inverting, vent to release excess pressure by carefully opening the stopcock.

 

    Shake, and vent the funnel intermittently for about 5 minutes.

 

    Allow the contents of the funnel to stand until the mixture has separated into two distinct

    layers.  If two layers do not separate, consult your instructor.

 

    Separate the layers and pour the aqueous layer into a 500-mL Erlenmeyer flask.

 

    Wash the organic layer with 10mL of water.

 

    Allow the contents of the funnel to stand until two distinct layers form.  Again, if two layers

    do not form,  consult your instructor.

 

    Separate the layers and add the aqueous layer to your 500-mL Erlenmeyer flask.

 

    Place the organic layer into your separatory funnel, and add to it

    10mL of 5% sodium bicarbonate.

 

    Swirl the contents of the separatory funnel gently, without the stopper in the funnel.

    After swirling for about 1 minute, stopper and invert the funnel.

 

    After inverting, vent to release excess pressure by carefully opening the stopcock.

 

    Shake, and vent the funnel intermittently for about 5 minutes.

 

    Allow the contents of the funnel to stand until the mixture has separated into two

    distinct layers.  If two layers do not separate, consult your instructor.

 

    Separate the layers and add the aqueous layer to your 500-mL Erlenmeyer flask.

 

    Wash the organic layer with 10mL of H2O.

 

    Allow the contents of the funnel to stand until the mixture has separated into two

    distinct layers.  If two layers do not separate, consult your instructor.

 

    Separate the layers and add the aqueous layer to your 500-mL Erlenmeyer flask.

 

    Transfer the organic layer to a 50-mL Erlenmeyer flask and add 1gm. anhydrous

    CaCl2 .

 

    Swirl the flask, intermittently for 15 minutes.

 

    Transfer your product to a tared sample bottle, appropriately labeled.  Save this

    product in your drawer for the alkyl halide tests.

 

    Turn in your product and lab reports for synthesis of 2-chloro-2-methylbutane and

    alkyl halide classification tests upon completion of the alkyl halide tests.


Notes

Steps 1-2:        The reaction, including mechanism is:


 

Steps 3-4:        Venting is necessary because HCl has a high vapor pressure.

 

Step 8: The washing with water is to remove any excess HCl.

 

Step 9: The washing with NaHCO3  is to neutralize the acid that is still

            present, ( i.e. HCl + NaHCO3 6 NaCl + H2CO3, which immediately disintegrates

            to CO2 and water.  Because CO28 gas is produced, venting is necessary.

 

Step 10:Water simply washes away the HCl and NaHCO3 that is still present.

 

 

 


Che 317         Sp’2005

 

Lab Report

 

 

 

Title: Synthesis of 2-Chloro-2-methylbutane

 

Name:

 

Date:

 

 

Equation:

 

 

 

 

 

Table of Physical Constants

Compound                           M.W.                          density                   bp/mp

(CH3)2C(OH)CH2CH3            88.15                           0.805                       102

 HCl                                           36.5                            1.2                          -----

(CH3)2C(Cl)CH2CH3              106.6                            0.866                         85

 

 

(CH3)2C(OH)CH2CH3

HCl

(CH3)2C(Cl)CH2CH3

MW

 

 

 

Moles

 

 

 

grams

 

 

 

density

 

 

 

mL

 

 

 

 

Results: Calculate the % yield for 2-chloro-2-methylbutane

 

 

 

Boiling range for your product                                                            to                     oC