Ch_322a_11.07

Ch_322a_11.07 - Some Observations on the Hydroboration...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
The Hydroboration-Oxidation Procedure Alcohols may be prepared from alkenes by the general two-step procedure of hydroboration-oxidation . Borane and Diborane Boron forms a trihydride, BH 3 , called borane . Because trivalent boron is electron-deficient, a dimer, B 2 H 6 , called diborane forms in the gas phase and non-associating solvents. 2 H-B H H borane B H H H B H H H diborane
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Laboratory Scale Reactions Diborane ignites in air . Commercial solutions of borane in tetrahydrofuran (THF) are much more stable, and allow laboratory procedures to be performed under an inert atmosphere (argon or nitrogen). B H H H B H H H diborane + 2 O : The nucleophilic THF associates with BH 3 to form a Lewis acid-base complex. B H H H O + - THF:BH 3 complex in THF solution
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 4
Background image of page 5
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Some Observations on the Hydroboration Reaction Stoichiometry all 3 H may react CH 3 CH=CH 2 + BH 3 CH 3 CH 2 CH 2 BH 2 propylborane CH 3 CH=CH 2 (CH 3 CH 2 CH 2 ) 2 BH dipropylborane CH 3 CH=CH 2 (CH 3 CH 2 CH 2 ) 3 B tripropylborane Regiochemistry the major addition product has boron attached to the less substituted carbon CH 3 CH 2 CH 2 CH 2 CH=CH 2 BH 3 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 BH 2 + CH 3 CH 2 CH 2 CH 2 CHCH 3 BH 2 (94%) (6%) CH 3 CH 2 C=CH 2 CH 3 BH 3 CH 3 CH 2 CHCH 2 BH 2 CH 3 CH 3 CH 2 CCH 3 CH 3 BH 2 (99%) (1%) Stereochemistry hydroboration is a syn-addition CH 3 BH 3 CH 3 H H BH 2 product of syn-addition...
View Full Document

Page1 / 5

Ch_322a_11.07 - Some Observations on the Hydroboration...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online