Why does butan-2-ol have no effect on plane polarised light?

Butan-2-ol can be produced as a result of reducing butanone with NaBH4. The hydride ion in NaBH4 is used as a nucleophile which can attack the C on the (C=O )either above or below the plane, depending on the orientation of the double bond. A dative covalent bond is formed. The double bond (C=O) is broken as electrons are transferred to the oxygen, leaving it negatively charged. There is thus an electrostatic attraction between the O- ion and an H+ ion, ultimately producing butan-2-ol. As the nucleophile can attack from above or below the plane, there is an equal probability that each of the two enantiomers of butan-2-ol will be produced in equal amounts, thus generating a racemic mixture. Regardless of the chiral centre in butan-2-ol, the equal amounts of opposing enantiomers means they will rotate plane polarised light in different directions by the same amount - cancelling their individual effects. Butan-2-ol is therefore not optically isomeric in this instance.

SK
Answered by Sunzida K. Chemistry tutor

7266 Views

See similar Chemistry A Level tutors

Related Chemistry A Level answers

All answers ▸

Why do branch chained isomers have lower boiling point than straight chain equivalents?


What are 'Rate equations' and why are they useful?


How can an aldehyde be distinguished from a ketone?


The reversible reaction of sulfur dioxide and oxygen to form sulfur trioxide is shown below. 2SO2(g) + O2(g) 2SO3(g) An equilibrium mixture contains 2.4mol SO2, 1.2mol O2 and 0.4mol SO3. The total pressure is 250atm. What is the p(SO3)?


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences