3,4-Dimethylpent-1-ene has the formula CH2=CH-CH(CH3)-CH(CH3)2  When pure (R)-3,4-dimethylpent-1-ene is

treated with hydrogen over a platinum catalyst, the product is (S)-2,3-dimethylpentane.

(a) Draw the equation for this reaction. Show the stereochemistry of the reactant and the product.

(b) Has the chirality center retained its configuration during this hydrogenation, or has it been inverted?

(c) The reactant is named (R), but the product is named (S). Does this name change imply a change in the spatial arrangement of the groups around the chirality center? So why does the name switch from (R) to (S)?

(d) How useful is the (R) or (S) designation for predicting the sign of an optical rotation? Can you predict the sign of the

rotation of the reactant? Of the product? (Hintfrom Juliet Capulet: “What’s in a name? That which we call a rose/By

any other name would smell as sweet.”)