Science quiz | Isomers: same formula, different persona

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Visual: Name this compound. It can exist in three forms, or isomers, as shown here, differing by the relative position of the two methyl groups (-CH3) attached to it.

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This hydrocarbon has the same formula as octa-1,3,5,7-tetraene but forces its carbon atoms to bond to each other at right angles, forming an almost perfect cube. Since carbon-carbon bonds don’t like this angle, the compound is famous for its extreme strain energy. Name this hydrocarbon.

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This square-planar platinum complex comes in two forms called cis and trans. Curiously, only the cis form is medically useful because it can crosslink DNA in cancer cells, killing them. Despite having an identical formula, the trans version is biologically inactive. Name the complex.

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This ring-shaped molecule with alternating double bonds is both aromatic and a building block of countless chemicals, from dyes to drugs. Its hexagonal symmetry made it the first molecule drawn with a circle inside a ring. Name it. Hint: It’s an isomer of 1,2,3-cyclohexatriene.

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This class of polycyclic aromatic compounds twist into screw-like shapes, showing chirality (or handedness) even though they contain no chiral centres. Their shapes make them optically active and useful in applications involving circularly polarised light, which increases contrast and reduces glare. Name the class.

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An isomer of naphthalene named for its deep blue hue, this compound defies expectations by having a dipole moment and a visible colour despite being aromatic — a contradiction. Its structure links a five-membered and a seven-membered ring that share electrons in an unusual way.