Organic Lab 7

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Amanda Jornd
Experiment 7-
Synthesis and Reactivity of tert-Butyl Chloride Via an SN1 Reaction Introduction/Background:
Alkyl halides are compounds in which a halogen atom replaces a hydrogen atom of an alkane. Alkyl halides are classified as primary, secondary or tertiary depending on the number of alkyl substituents directly attached to the carbon attached to the halogen atom. The purpose of this lab was to properly prepare t-butyl chloride from t-butyl-alcohol in a concentrated hydrochloric acid. The reaction occurs through a nucleophilic substitution, which is when a nucleophile replaces the leaving group in the substrate. In this lab, the hydroxyl group of t-butyl alcohol is replaced by a chlorine atom. The reaction proceeds through an SN1 mechanism (Weldegirma 38-41).

“A nucleophile is any neutral or uncharged molecule with an unshared pair of electrons. In the substitution reaction, the nucleophile donates an electron pair to the substrate, leading to the formation of a new bond to the nucleophile, while breaking the existing bond to the leaving group” (Solomons and Fryhle 99-102). The two types of nucleophilic substitution reactions, SN1 and SN2, are identified based on whether the different steps occur simultaneously (SN1) or in two separate steps (SN2). To synthesize the t-butyl chloride, the t-butyl alcohol goes through an SN1 reaction. Also, the nature of the solvent can affect which substitution reaction will occur. Polar protic solvents typically favor SN1 reactions. This is because the SN1 mechanism is carried out in two steps and the polar protic solvent produces both a cation and an anion which are capable of stabilizing the charges on the ions formed during the reaction. Because an SN2 reaction occurs in one step, this is unfavorable; however, the SN2 reactions tend to favor polar aprotic solvents. Another factor affecting the type of substitution reaction is the nature of the leaving group. Since the SN1 reactions occur in one step, they generally require an excellent leaving group and won’t typically run with a poor leaving group. The SN2 reaction also favors excellent leaving groups but can run with any type of leaving group because it is run in two different steps. To synthesize the t-butyl chloride, the t-butyl alcohol goes through an SN1 reaction. (Weldegirma 38-41). Mechanism of the preparation of tert-butyl chloride:

Possible side reaction during the preparation of tert-butyl chloride:

Experimental Section/Flow Chart:
Part 1:
60mL separatory funnel
+ cooled 15mL of concentrated HCl to 0˚C
+ added 15mL of HCl to separatory funnel
+ added 5mL tert-butyl alcohol
+swirled it without the stopper for 20 minutes
+ let stand until two distinct layers were formed
+ drained lower layer into Erlenmeyer flask and saved just incase Organic Layer- in separatory funnel
+added 30mL of DI water
+ swirled for a few minutes
+ let stand until two distinct layers formed
+ drew off lower layer into Erlenmeyer flask and saved just incase Organic Layer- in separatory Funnel
+ added 15mL of 5% sodium bicarbonate
+ shook with stopper with venting
+ let stand for a few minutes until two distinct layers formed
+ drew off lower layer into Erlenmeyer flask and kept just incase Organic Layer- in separatory funnel
+ added 15mL of water
+ swirled for a couple minutes
+ let stand until two distinct layers have formed
+ drew off lower layer into Erlenmeyer flask and kept just incase Organic Layer
+ transferred product layer into clean/dry 125 mL Erlenmeyer flask
+ added 1.5 grams of anhydrous calcium chloride to dry the product
+decanted into round bottom flask
+ added 6 boiling stones
+ ran through a simple distillation
Tert-Butyl Chloride
Part 2-
Test tube #1-
+ added .1mL tert-butyl chloride from part 1
+ added 1mL of NaI
+ shook while holding top of test tube with finger
+ recorded time, look, color, etc.
Negative Result
Test Tube #2-
+...
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