Chemist publish "best of" table for yields etc. These represent the one time they did the reaction and it worked well. Perhaps it was a particularly dry day...We should really start publishing yields with error bars and SD.
Chemist publish "best of" table for yields etc. These represent the one time they did the reaction and it worked well. Perhaps it was a particularly dry day...We should really start publishing yields with error bars and SD.
some of them . this is true unfortunatly .but in the other side there are a good researchers write exactly procedure with detials. this is our life you can see the bad and good things in the same time .
I think a good appreciation of reliable is "does it work at all" rather than the exact yields which can fluctuate due to the extremely large number of variables.
Often the yields relate to neglected conditions that aren't explicitly mentioned. Examples are the addition or exclusion of ambient light, recognising that room temperature means different things in different places or different times of the year, rates/orders/concentration of addition, whether it adds down the side of the flask or drops in the middle, stirring rates, homogeneity, reagent/reactant/solvent sources/states/age, the importance of trace water/peroxides, trace metals on stirrer bars, whether or not sulfur has been used in the lab recently.
I know someone who could only get their hydrogenation to work in high yields if they accidentally set their catalyst on fire at least once. Maybe he just liked fire.
This level of detail is far beyond simply writing good procedures.
At a more fundamental level, the yields, whilst practical and potentially useful, mean little about the actual validity of the chemistry involved.
It is also the easiest information to falsify which is probably quite common given the often high pressure environment placed on students and supervisors. There is a saying that I have heard called the "Corey 1,2- rearrangement" whereby an 18% yield is magically rearranged into an 81% yield.
Yes, I have experienced the same for several times when I performed the experiments by following reported reaction conditions. Either yields or reaction time are not reprodusable in organic synthesis. If you consider the same in the filed of nano chemistry, you may not able to reproduce the morphology or surface area of reported nano materials. This is may be due to the small modifications while reporting the experimental procedures or may be handling problems with person to person.
Many times the structural facture will govern the reactivity i.e. elecron donating & electron withdrawing groups. Hence , the gereral procedure is some times is not working
See the referance in the chemistry part and also try reproduce some derivative as if u validated the methods by ur self if the m.p is right dont deal with yield sometimes it may be enlarged by the authors due to reviewers comments also see the orginal reaction in organuc syntheses will be more accurte wish this will help
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