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ASChemistryOCRExam Questions4. Core Organic Chemistry4.6 Organic Synthesis

Organic Synthesis (OCR AS Chemistry)

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4.6 Organic Synthesis

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4.6 Organic Synthesis

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11 mark

The preparation of organic liquids, such as some esters, can involve heating under reflux.

Which statement about heating under reflus is correct?

  • Organic liquids can be heated without evaporation taking place.

  • Organic liquids can be maintained at their boiling point for extended periods.

  • Heating is carried out using a water bath.

  • The apparatus is closed to prevent the loss of any materials.

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21 mark

Which of the following can be done with the aid of a separating funnel?

  Neutralise acidic impurities Dry organic liquids Separate miscible liquids
A ✓ ✓ ✓
B ✓ ✓ X
C X ✓ ✓
D ✓ X X

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    31 mark

    What reaction could the following equipment be used for?

    distillation

    • Preparing a carboxylic acid.

    • Cracking an alkane.

    • Oxidising an alcohol.

    • Halogenation of an alkene.

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    41 mark

    What is the purpose of the part labelled X in the diagram?

    distillation---thermometer-labelled-x

    • To check the boiling point of the reaction mixture.

    • To separate the distillate from the reaction mixture.

    • To check the purity of the distillate.

    • To prevent gases from escaping.

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    51 mark

    Which type of reaction has the greatest atom economy?

    • Substitution

    • Hydrolysis

    • Elimination

    • Addition

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    61 mark

    Which reaction occurs when ethane and chlorine are mixed in the presence of sunlight?

    • A free-radical substitution with hydrogen produced

    • A free-radical substitution with hydrogen chloride produced

    • A free-radical substitution with no gas produced

    • A nucleophilic substitution with hydrogen chloride produced

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    71 mark

    This molecule is responsible for the flavour of spearmint chewing gum.

    functional-group-mechanisms

    What is a true statement about the functional groups 1 or 2?

    • 1 will undergo electrophilic addition

    • 1 will undergo electrophilic substitution

    • 2 will undergo nucleophilic substitution

    • 2 will undergo electrophilic substitution

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    81 mark

    The addition of hydrogen bromide, HBr, to pent-2-ene, CH3CH2CH2CH=CH2 , produces

    • 1-bromopentane

    • 2-bromopentane

    • 1,2-dibromopentane

    • A mixture of 1-bromopentane and 2-bromopentane

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    91 mark

    A reaction scheme is shown below. 

    major-and-minor-product

    Which of the following statements is correct?

    • Product 1 is the major product

    • Product 2 is the major product

    •  A 50:50 mixture of the two products is formed

    • The bromine acts as an electrophile

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    101 mark

    A reaction sequence is shown below. 

    reaction-sequence

    Identify reaction 1 and 2. 

      Reaction 1  Reaction 2 
    A Nucleophilic Addition Oxidation
    B Nucleophilic Substitution Oxidation
    C Nucleophilic Addition Reduction
    D Nucleophilic Substitution Reduction

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      11 mark

      Crotonaldehyde, CH3CH=CHCHO, occurs in soybean oils and can be formed from its alcohol.

      What are the reagents and conditions required to form crotonaldehdye from its alcohol?

        Reflux Distillation K2Cr2O7  K2Cr2O7 / H+ 
      A ✓ X ✓ X
      B ✓ X X ✓
      C X ✓ X ✓
      D X ✓ ✓ X

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        21 mark

        Which of the following reagents can be used to dry a damp sample of ethyl ethanoate?

        • Saturated sodium carbonate solution.

        • Anhydrous sodium sulfate.

        • Concentrated sulfuric acid.

        • Aluminium oxide.

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        31 mark

        Which molecule contains an aldehyde functional group?

        • CH3CH2CH2COOCH3 

        • CH3CH2CH2COCH3 

        • CH3CH2OCH2CH3 

        • CH3CH2CH2CH2CHO

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        41 mark

        Which haloalkane contains a tertiary carbon atom?

        • CH3CH2CH2Cl

        • CH3CH2CH(CH3)Br

        • C(CH3)3Cl

        • CH3CHBrCH2CH3 

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        51 mark

        Butanoic acid can be synthesised using the following two-step reaction scheme.

        straight C subscript 4 straight H subscript 9 Br rightwards arrow with Step space 1 on top straight C subscript 4 straight H subscript 9 OH rightwards arrow with Step space 2 on top straight C subscript 3 straight H subscript 7 COOH

        What is the correct classification of the steps?

          Step 1 Step 2
        A Substitution  Addition
        B Oxidation Substitution
        C Addition Oxidation
        D Substitution Oxidation

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          61 mark

          What reagents and conditions are required for the following two-step synthesis of propanal?

          1-chloropropane rightwards arrow with Step space 1 on top Propan-1-ol rightwards arrow with Step space 2 on top Propanal

            Step 1 Step 2
          A Reflux with NaOH (aq) Distil with K2Cr2O7 
          B Reflux with NaCN (aq) Reflux with K2Cr2O7 / H+ 
          C Distil with K2Cr2O7 / H+  Reflux with NaCN (aq)
          D Reflux with NaOH (aq) Distil with K2Cr2O7 / H+ 

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            71 mark

            Butanone can be produced from but-2-ene by the following two-step synthesis of propanal.

            But-2-ene rightwards arrow with Step space 1 on top INTERMEDIATE rightwards arrow with Step space 2 on top Butanone

            Step 1 uses a phosphoric acid catalyst and steam.

            What is the intermediate?

            • Butan-1-ol

            • Butan-2-ol

            • Butan-2,3-diol

            • Butanoic acid

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            81 mark

            The structure of a compound used to treat attention deficit hyperactivity disorder is shown below.

            ocr-4-6m-q8

            Which functional group(s) is / are in a molecule of the compound?

            1. Amine
            2. Carboxylic acid
            3. Ketone

            • 1, 2 and 3

            • Only 1 and 2

            • Only 2 and 3

            • Only 1

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            91 mark

            Ethane-1,2-diol can be made from ethene using the following two-stage synthetic route.

            H2C=CH2 rightwards arrow with Step space 1 on top BrCH2CH2Br rightwards arrow with Step space 2 on topCH2OHCH2OH

            What reagents are required for each step?

              Step 1 Step 2
            A Excess HBr (aq)  Ethanolic NaOH
            B Br2 (aq) C2H5OH (l)
            C H2 (g) with a Ni catalyst NaOH (aq)
            D Br2 (aq)  NaOH (aq)

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              101 mark

              Ethane-1,2-diol can be made from ethene using the following two-stage synthetic route.

              H2C=CH2 rightwards arrow with Step space 1 on top BrCH2CH2Br rightwards arrow with Step space 2 on topCH2OHCH2OH

              What are the mechanisms involved in each step?

                Step 1 Step 2
              A Electrophilic substitution  Electrophilic addition
              B Electrophilic addition Nucleophilic substitution
              C Electrophilic addition Nucleophilic addition
              D Nucleophilic substitution Electrophilic addition

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                11 mark

                Which statements about the preparation and purification of an organic liquid is/are correct?

                1. Reflux is used for the condensation reaction between an alcohol and a carboxylic acid.
                2. In a separating funnel, adding water will identify the organic layer as it will decrease in volume.
                3. A bunsen burner must be used in reflux because it requires more vigorous heating.

                • 1, 2 and 3

                • Only 1 and 2

                • Only 2 and 3

                • Only 1

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                21 mark

                Alcohol is produced by the following 2-step process.

                Methylbutane rightwards arrow with bold Step bold space bold 1 on top Intermediate X begin mathsize 16px style rightwards arrow with bold Step bold space bold 2 on top end style Alcohol

                Upon addition of acidified potassium dichromate(VI), the alcohol produces an orange solution.

                Which row correctly identifies intermediate X and the reagents/conditions of step 2 in this process?

                 

                 

                Intermediate X

                Reagents/conditions of step 2

                A

                2-chloro-2-methylbutane

                NaOH (aq) / reflux

                B

                2-methylbut-1-ene

                NaOH (aq) / reflux

                C

                3-methylbut-1-ene

                Steam and H2SO4 / heat

                D

                2-chloro-3-methylbutane

                Steam and H2SO4 / heat

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                  31 mark

                  1-chlorobutane can be made by the following multistep process.

                  Which of the following reagents is not suitable for the indicated step?

                  vuqMYbi5_ocr-as-4-6h-mcq-q3-reaction-sequence

                  • Step 1 hot K2Cr2O7/H2SO4

                  • Step 2 hot Al2O3

                  • Step 3 H2 and Ni catalyst

                  • Step 4 Cl2 and UV light

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                  41 mark

                  Which of the following types of reaction is not involved in the sequence below?

                  rJyXzIce_ocr-as-4-6h-mcq-q4-reaction-sequence

                  • Electrophilic addition

                  • Elimination

                  • Nucleophilic substitution

                  • Free radical substitution 

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                  51 mark

                  Which of the following statements is/are correct?

                  1. The sequence alkene → alcohol → aldehyde has a higher yield than alkene → haloalkane → alcohol → aldehyde.
                  2. A nucleophile will attack a haloalkane because the halogen atom is more electronegative than the hydrogen atoms.
                  3. Polyethene is not degraded by NaOH because of the electron-rich carbon-carbon double bonds.

                  • 1, 2 and 3

                  • Only 1 and 2

                  • Only 2 and 3

                  • Only 1

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