Question

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3. Explain the difference in reactivity between organolithium reagents (eg CH Li) and grignard reagents (e.g CHMOX). In other words, which one is more reactive and why? hos Molecular Weight 181.31 Molecular Weight: 106.55 Density: 1.03 g/mL Molecular Weight: 226.32 4. In the above reaction, assume that you plan to use 0.5 mL of the starting acid chloride with 10 mL of 1.0 M phenylmagnesium bromide. Which would be the limiting reagent? What is the theoretical yield of this reaction? (Hint: to figure out how many moles of grignard, pay attention to the units of molarity and volume given.) 5. What would the percent yield of the previous reaction be if you obtained 91 mg of product?

Answer 1

Ans. The organo- lithium reagents are more reactive than organo-magnesium halides and can act as both nuclieplice and a base. Sinice lithuim is more electropositive than magnesum which makes Li -C bond more polar than Mg-C making it more reactive. eg:- when ketones are sterically hindered, using gerignard reagent leads to reduction of carbonyl guoup instead of addulion Thowever, alkyllithiumi reagents are less likely to reduce the ketone and may be used to synthesize substituted alcohols. 011 To C₂H5 Mg I , OH - C₂H5 BASSY

Any moliy of aud chloride = ? volume of acid chloride = 0.5 mL density of and chlorude = 1.03gime man - volume x densiter " 01516x 103 Žime = 0.5159 - Moles= man Molar mass 0.515g 106:55 gmol 1 Moles of acid chloride = 0.00 4833 mol Moles of Molarity & volume inh phenyemagnesium = bromice - = 100M X 0.012 0.01 mol - Now 1 mol acid chloride need I mol phenyl mamesium bromide 0.00.4833 mol require -0.004833 mol phenyl magnesuno comide We have 0.01 mol of phenylmagnesum bromide, this it is in encen. acid chloride is limiting reagent.

Moles of acid chloride = 1 I mol acid chloride guie 0.005 mol will give 0.004833 mol ñ .005 mol - I mol product - 0.005 mol product Moles of product = 0.005 mol Man = Mole x Molor man = 0.005 mol x 226-32 gnol = 1:1316 g = 113 1.6 mg so theoretical yield = 1131.6 mg 5. observed yield = aling % yield = Observed yelld theoretical yield =alng e yuld xloo T316 my X 100 = 8.04% Percentage yield=8%