Mr Cole Chemistry

Synthesis Pathways Questions 1

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  1. The following pathway has two steps missing.
    1. Draw the skeletal formulae of the two missing molecules.
    2. State the reagents and conditions of the second step in the synthesis.
    3. Outline the mechanism for the first step in the synthesis.
    4. State what effect the final product has on plane polarised light and explain your answer.
  2. The following pathway has a missing step.
    1. Draw the skeletal formula of the missing molecule.
    2. State the name of the mechanism for the first step.
    3. State the conditions and reagents for the first step.
    4. Outline the mechanism of the second step.
  3. The following pathway has two missing steps. The first reaction is between an organic molecule and chlorine in the presence of UV light.
    1. Draw the skeletal formulae of the two missing molecules.
    2. Outline the mechanism of the second step in the pathway.
    3. One of the steps can result in impurities in the final product. State which step this is and explain why this is the case.
  4. The following pathway is missing two steps. The final step does not involve any reagents other than the molecule shown in box three. The Mr of the final product is 85.10.
    1. Draw the skeletal formulae of the missing molecules.
    2. State the reagents and conditions for reaction 2.
    3. The first step steps in reaction 2 have been outlined but the curly arrows and lone pairs are missing. Add them into the diagram.
    4. An alternative product that has an Mr of 170.21. Draw the skeletal formula.
  5. The following pathway is missing two steps. Step 3 is the reaction between the organic molecule and potassium hydroxide in ethanolic conditions.
    1. Draw the skeletal formula of the missing molecules.
    2. State the reagents for step 1.
    3. Name the molecule in the third box.
  1. The following pathway has two steps missing.
    1. Draw the skeletal formulae of the two missing molecules.
    2. State the reagents and conditions of the second step in the synthesis.
      Acidified potassium dichromate, warm.  
    3. Outline the mechanism for the first step in the synthesis.
    4. State what effect the final product has on plane polarised light and explain your answer.
      No effect. While the product is chiral, you get a racemic mixture (50/50 mix of the two enantiomers). This is because the carbonyl is planar. This means that when the CN– ion attacks the carbon, it can attack it from above or below. It attacks from both angles with equal probability, resulting in equal amounts of the two enantiomers.
  2. The following pathway has a missing step.
    1. Draw the skeletal formula of the missing molecule.
    2. State the name of the mechanism for the first step.
      Electrophilic substitution
    3. State the conditions and reagents for the first step.
      2-chloroethylamine, aluminium chloride catalyst
    4. Outline the mechanism of the second step.
  3. The following pathway has two missing steps. The first reaction is between an organic molecule and chlorine in the presence of UV light.
    1. Draw the skeletal formulae of the two missing molecules.
    2. Outline the mechanism of the second step in the pathway.
    3. One of the steps can result in impurities in the final product. State which step this is and explain why this is the case.
      Step 1 – free radical substitution is an unreliable method of chlorinating alkanes. You could end up with 1-chlorobutane instead of two chlorobutane, or multiple chlorinated butane, such as dichlorobutane or trichlorobutane.
  4. The following pathway is missing two steps. The final step does not involve any reagents other than the molecule shown in box three. The Mr of the final product is 85.10.
    1. Draw the skeletal formulae of the missing molecules.
    2. State the reagents and conditions for reaction 2.
      LiAlH4 in dry ether or H2 and a Ni catalyst.
    3. The first step steps in reaction 2 have been outlined but the curly arrows and lone pairs are missing. Add them into the diagram.
    4. An alternative product that has an Mr of 170.21. Draw the skeletal formula.
  5. The following pathway is missing two steps. Step 3 is the reaction between the organic molecule and potassium hydroxide in ethanolic conditions.
    1. Draw the skeletal formula of the missing molecules.
    2. State the reagents for step 1.
      chlorine
    3. Name the molecule in the third box.
      butane-2,3-diol
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