Q.Define racemic mixture. Give IUPAC name of the compound whose condensed structural formula is printed as: (the branch is drawn on a vertical bond above the CH carbon).
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Start your 14-day free trial to unlock the full solution →Racemic mixture = 1:1 enantiomer pair, optically inactive by cancellation; the drawn aldehyde is 2-methylbutanal.
Racemic mixture: when a chiral (optically active) compound is synthesised by an ordinary (non-stereoselective) laboratory reaction, it is usually obtained as an equimolar mixture of its two mirror-image forms — the dextrorotatory (d- or ) and levorotatory (l- or ) enantiomers. Although each pure enantiomer individually rotates plane-polarised light, in a 50:50 mixture the rotation caused by the d-form is exactly cancelled by the equal and opposite rotation of the l-form, so the mixture as a whole shows zero net optical rotation — it is optically inactive by external compensation, and is called a racemic mixture or racemate (often denoted or -).
IUPAC name: the structure is a 4-carbon chain bearing an aldehyde group, with a methyl branch on the carbon next to the carbon. Numbering from the aldehyde carbon (C1, which must get the lowest locant as the principal characteristic group):
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