Don't Forget the Workup

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Don ’ t Forget the Workup

Andrew P. Dicks*

Department of Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3H6

ABSTRACT:

Emphasis is placed on thoroughly considering the workup of a reaction used to promote principles of green chemistry to undergraduates.

KEYWORDS:

Second-Year Undergraduate, Upper-Division Undergraduate, Laboratory Instruction, Organic Chemistry, Hands-On Learning/Manipulatives, Green Chemistry, Organometallics, Synthesis

D uring the past decade, the Nobel Prize-winning Suzuki reaction

¹

has been heavily used as a vehicle to teach fundamental green chemistry principles.

²⁻⁹

As examples, through performing a Suzuki coupling, undergraduates have learned about aqueous reactivity,

^2,5⁻⁹

energy-e

ﬃ

cient con- ditions,

³

greener reaction solvents,

⁴

and catalyst recycling.

⁸

A recent article in this Journal explored use of microwave heating as a more sustainable technology in the context of a Suzuki biaryl synthesis.

²

While this latter methodology is to be applauded, it is worth underscoring that there are many factors impacting the

“

greenness

”

of a laboratory process. Mercer et al. have described a multivariate metric exercise requiring students to determine the environmental impact of several organic syntheses.

¹⁰

In this approach, a reaction workup is considered as carefully as the transformation that precedes it. The microwave-assisted aqueous Suzuki reactions outlined by Soares et al. have problematic workups from a green chemistry perspective, as they involve (i)

ﬁ

ltration through Celite; (ii) liquid

−

liquid extraction using dichloromethane; and (iii)

ﬂ

ash- column chromatography.

²

While these three steps may be necessary to obtain puri

ﬁ

ed products in acceptable yields, instructors have a duty to emphasize the

“

non-green

”

aspects of any experiment used in green chemistry teaching, so that improvements might be suggested. This was concisely proposed by Goodwin in the form of three student laboratory report questions:

¹¹

• “

What was green about the experiment?

”

• “

What was not green?

”

• “

How could the experiment be made greener?

”

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AUTHOR INFORMATION Corresponding Author

*

E-mail: [email protected].

Notes

The authors declare no competing

ﬁ

nancial interest.

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Letter pubs.acs.org/jchemeduc

Division of Chemical Education, Inc. A DOI: 10.1021/ed5008712

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