Convert (r)-2-butonal to (s)-s-butonal

[bjon-07]

Please Help!

How do I convert (r)-2-butonal to (s)-s-butonal using toluenesulfonyl chloride tosyl chloride (tsCL) as a replacment leaving group sense -OH is such a poor leaving group.

I can normal preform this kind of reaction, if the nuclelophil is different than the orginal leaving group. I got to the point where i have (R)-2-butyl tosylate.

The leaving is TsO- I want to convert this into HO-. How should I do this? Should I add an protic acid, or Na OH.


BTW why do SN2 reaction invert the configuration. I am having a hard time visualling why they invert configuration.

 

[chem_tr]

See Walden's inversion in your textbook, this is the solution. SN₂ types of reactions involve configuration change, since first ion hits the center of the second, and configuration changes. We usually give the example of upside-down umbrella to better realize in your minds. An umbrella goes upside down when a strong wind appears. SN₂ reactions are similar to this analogy.

Tos-Cl + R-OH \longrightarrow Tos-OH + R-Cl
R-Cl + NaOH \xrightarrow{heat, phase~transfer~catalyst} R-OH + NaCl