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Chemistry: Organic Chemistry Fundamentals 1 Flashcards

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  1. Which of the following compounds is classified as an ester?

    Answer: CH₃COOCH₂CH₃

    CH₃COOCH₂CH₃ (ethyl ethanoate) contains the ester functional group –COO–, formed by the condensation of a carboxylic acid and an alcohol. CH₃COOH is a carboxylic acid, CH₃OCH₃ is an ether, and CH₃CH₂OH is an alcohol.

  2. Propene (CH₃CH=CH₂) reacts with HBr. According to Markovnikov's rule, what is the major product?

    Answer: CH₃CHBrCH₃

    Markovnikov's rule states that in electrophilic addition to an unsymmetrical alkene, H⁺ adds to the carbon bearing the greater number of hydrogen atoms, so Br⁻ adds to the more substituted carbon (C-2), giving 2-bromopropane as the major product.

  3. How many structural isomers does the molecular formula C₄H₁₀ represent?

    Answer: 2

    C₄H₁₀ has exactly two structural isomers: n-butane (CH₃CH₂CH₂CH₃), a straight chain, and 2-methylpropane (isobutane, (CH₃)₃CH), a branched chain. No other connectivity is possible for four carbons with the saturated formula.

  4. Which reagent can be used in the laboratory to distinguish an alkene from an alkane?

    Answer: Bromine water (Br₂/H₂O)

    Alkenes rapidly decolorise bromine water through electrophilic addition across the C=C double bond, turning the orange-brown solution colourless. Alkanes do not react with bromine water under normal conditions and the colour is retained.

  5. Which monomer undergoes addition polymerisation to produce the polymer polyethylene (polythene)?

    Answer: Ethylene (CH₂=CH₂)

    Addition polymerisation requires a monomer with a C=C double bond. Ethylene (CH₂=CH₂) contains a double bond that opens repeatedly to link thousands of monomer units into the –(CH₂CH₂)ₙ– chain of polyethylene. The other options lack a polymerisable double bond.

  6. Ethanol is heated with excess concentrated H₂SO₄ at 170 °C. What is the primary organic product?

    Answer: Ethylene (CH₂=CH₂)

    At 170 °C, concentrated H₂SO₄ promotes intramolecular dehydration (elimination) of ethanol, removing H₂O across the C–C bond to yield ethylene. At the lower temperature of 140 °C, intermolecular dehydration instead produces diethyl ether; temperature is the key distinguishing condition.