From: Jack Kellum (jkellum$##$ucsd.edu)
Date: Mon Feb 28 2000 - 14:45:46 EST
It would be interesting in general to compare pre-workup yields to
post-purification yields in order to determine loss and thus, whether
workup/purification conditions can be changed so as to minimize the loss (if
any). But a yield reported in a journal should reflect what the next
experimenter can hope to obtain in a similar reaction. IMHO, the only
meaningful yield is what you have in your hands after purification. As to
inflated yields, I've heard this before also. But one should keep in mind
that generally the reported yield is the best yield obtained in several
different reactions. I've personally had the experience of a small-scale
reaction (~50 mg s.m.) result in a much higher yield than the same reaction
repeated on a 1 gm scale.
Jack Kellum
Department of Chemistry and Biochemistry
University of California, San Diego
----- Original Message -----
From: "antonio regla" <areglac$##$yahoo.com>
To: "Multiple recipients of list orglist" <orglist$##$dq.fct.unl.pt>
Sent: Monday, February 28, 2000 11:16 AM
Subject: ORGLIST: Re: Pre-Work-Up Yields
Dear List Members:
Does anyone know of a good literature reference on
ways to determine pre-work-up yields in organic
reactions? Usually it is very hard to reproduce
literature yields, they are too high most of the
times, which makes some of us think if the yield
reported is the isolated yield or before work-up. Some
journals are very strict and require authors to
specify which yields they are referring to, but others
are not strict about it. The nature of reaction
mixtures is usually quite complex, as one finds
multiple phases, a mixture of by-products of unknown
origin, ionic and covalent products. Are there any
guidelines in the literature on how to analyze such
mixtures as to determine the yield of the desired
product. I have been told by some grad students that
in order to please their research advisors sometimes
they exaggerate the yields, which in my view is
nothing more than cheating. I would like to recommend
the practice of determining pre-work up yields, and I
will appreciate any information you may have regarding
this issue.
Thanks in advance for your help.
Sincerely.
Antonio Regla
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