What are some non-human sources of error for a two part lab studying substitutio

Question

What are some non-human sources of error for a two part lab studying substitution reactions? (3-5)

The first part was the synthesis of t-butyl chloride from t-butanol and hydrochloric acid through an SN1 reaction.

The second part was the synthesis of 1-bromobutane from 1-butanol and sodium bromide through an SN2 reaction.

Both reactions had a very low percent yield. I've included pictures of the procedure for both parts

SN1:

SN2:

PROCEDURE Part i Synthesis of tert-butyl chloride Obtain and wear goggles. Protect your arms and hands by wearing a long-sleeve lab coat and gloves. Conduct this reaction in a fume hood 2. Obtain 15 mL of concentrated hydrochloric acid using a graduated cylinder and carefully transfer to a 50 mL Erlenmeyer flask. CAUTION: Handle the hydrochloric acid with care Can cause painful burns if it comes in contact with the skin 3. Prepare an ice water bath in a 250 mL beaker and cool the flask containing the acid. 4. Set up the reaction in a separatory funnel. a. Clamp the support ring onto a ring stand, place the separatory funnel into the ring, and insert a funnel b. Carefully transfer the cooled acid to the separatory funnel. c. Measure 5.0 mL of tert-butanol and transfer to the separatory funnel. 5. Swirl the solution in the separatory funnel for five minutes. Note: Leave the funnel uncapped as you swirl to allow the gases to escape. 6. cap the separatory funnel, invert it, (e Make sure cap fits tightly before inverting the funnel) and immediately open the stopcock to release the pressure. When venting the funnel, point the tip towards the back of the fume hood and open the stopcock to release the pressure. 7. Shake the funnel for 15 minutes. Vent occasionally to prevent pressure buildup 8. Place the funnel in the support ring and allow thc solvent and aqucous layers to separate. Leave the funnel uncapped. 9. Drain the lower aqueous layer into a 125 mL Erlenmeyer flask. Be sure to label the flask as waste. 10. Prepare to wash the solution. a. Wash the organic layer with 30 mL of a saturated sodium bicarbonate solution. Add the sodium bicarbonate solution slowly. Swirl the funnel several times until the bubbling has stopped. b. Cap the funnel, invert, shake, and immediately vent. **Make sure cap fits tightly before inverting the funnel c. Place the uncapped funnel in the support ring and allow the layers to separate. d. Drain the aqueous layer into the waste beaker.

Explanation / Answer

SN1:

Prior to the distillatillaion, the condenser was checked and ensured that there was water running through. After some time, the water supply might have stopped. So, the gaseous t-Butylchloride, instead of condensing at the condenser, might have escaped out because there was no more water running. Therefore the yield % is less.

SN2:

The polar protic nature ofthe alcohol (H2SO4) discourages the SN2 mechanism because of its bulky size and relative weakness as a nucleophile. And to wash out the impurities we should use cold concentrated H2SO4. May be this wasn't done. So, because of the impurities the yield % was less.

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