Q.Choose the correct option.
Which of the following compound has highest boiling point?
a. n-pentane b. iso-butane c. butane d. neopentane

Because carbon and hydrogen have almost identical electronegativity, alkanes are essentially non-polar molecules held together only by weak van der Waals (London dispersion) forces, whose strength scales directly with how much surface area two neighbouring molecules can bring into contact. A straight-chain alkane, able to lie alongside its neighbours over its full length, therefore has stronger intermolecular attraction -- and correspondingly higher melting and boiling points -- than a more compact, branched isomer of the same molecular formula. This same non-polarity explains why alkanes are insoluble in water (a polar solvent) but freely soluble in non-polar organic solvents such as chloroform or ether. Alkanes are colourless and odourless, and their physical state at room temperature tracks chain length in a simple progression: the first four (methane to butane) are gases, roughly C5 to C17 are liquids, and C18 upward are solids.