Reactivity of halogenoalkanesEdexcel International A Level Chemistry: Flashcards

Exam questions on Reactivity of halogenoalkanes

1. A student compares the rates of hydrolysis of 1-chlorobutane, 1-bromobutane and 1-iodobutane. A few drops of each halogenoalkane are added to separate test tubes containing aqueous silver nitrate in ethanol, held in a water bath at 60 °C, and the time for a precipitate to appear is measured.
   Explain the order of the rates of hydrolysis of the three compounds in terms of bond enthalpy.2 marks
2. A technician compares three isomers of C₄H₉Br: 1-bromobutane, 2-bromobutane and 2-bromo-2-methylpropane. Equal volumes of each are added to separate tubes of aqueous silver nitrate in ethanol at the same temperature, and the time for the first precipitate is recorded.
   The precipitate appeared after 15 s for 2-bromo-2-methylpropane and after 300 s for 1-bromobutane. Calculate how many times faster the tertiary isomer reacted, and state one variable that had to be kept constant.2 marks
3. A student prepares 2-chloro-2-methylpropane by shaking 2-methylpropan-2-ol with concentrated hydrochloric acid in a separating funnel. The product is a colourless liquid that is immiscible with water. Its density is 0.84 g cm⁻³, the aqueous acid layer has a density of about 1.1 g cm⁻³, and the product boils at 51 °C.
   After shaking and standing, two layers form. State which layer is the organic product, explain how you know, and describe what the student then does to the other layer.3 marks