REAC0714: Seudying SNI and SN2 Racsions Nucleophilic Subesunice Pre-Laboratory A
ID: 557806 • Letter: R
Question
REAC0714: Seudying SNI and SN2 Racsions Nucleophilic Subesunice Pre-Laboratory Assignment 1. Why should care be exercised in handling concentrated acids such as H SO, and H 2. Why do primary alkyl halides typically undergo Sy2 substitution reactions more rapidly than do secondary or tertiary alkyl halides? 3. Why should reflux of the microscale reaction mixture be gentle, with the condensation ring remaining close to the surface of the liquid in the test tube? 4. By observing the reaction mixture, what visual evidence can be gained to indicate that 1-butanol is being converted to 1-bromobutane? 5. What is the function of anhydrous CaClh in this experiment?Explanation / Answer
1) Concentrated acids are very corrosive and dangerous chemicals that are commonly encountered in the laboratory. Some acids are also shock sensitive and when subjected to improper handling they can explode. Concentrated acids may be fatal if inhaled; and can cause severe eye and skin burns, severe respiratory and digestive tract burns. Contact with other materials may cause a fire. All operations involving concentrated acids MUST be conducted in the fume hood and the investigator MUST wear appropriate PPE.
2) Primary alkyl halides generally undergo SN2 mechanisms because (a) 1° substrates have little steric hindrance to nucleophilic attack and (b) 1° carbocations are relatively unstable. While in secondary or tertiary alkyl halides steric hindrance will be more and carbocation will be relatively stable which will result in less reaction.
3) The reflux of the microscale reaction mixture should be gentle, with the condensationring remaining close to the surface of the liquid in the test tube, to prevent the risk of theliquid bubbling out of the tube, thus avoiding the loss of HBr.
4) The formation of one layer instead of two , depends on the solvent (you didn't give details of what was in the tube exactly). Or Assuming that the reaction is done as an aqueous reaction, formation of 1-bromobutane would result in the formation of a second liquid layer because 1-bromobutane is not very soluble in water.
5) Anhydrous calcium chloride acts an agent to ensure a dry environment since it removes moisture by binding or adsorbing to water (making water less available).This is because the production of ethyl acetate from ethly alcohol also produces water and the reaction is in equilibrium. Removing water would shift the equilibrium in favor of the production of ethyl acetate. If water is not removed, yield of ethyl acetate would be low.
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