tag:blogger.com,1999:blog-8964719845369935777.post5604290306628973135..comments2024-03-29T09:05:29.819-04:00Comments on Chemjobber: Process Wednesday: yield versus timeChemjobberhttp://www.blogger.com/profile/15932113680515602275noreply@blogger.comBlogger7125tag:blogger.com,1999:blog-8964719845369935777.post-6401338941802796942014-11-18T14:35:48.717-05:002014-11-18T14:35:48.717-05:00I think I'd like to get this book.I think I'd like to get this book.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8964719845369935777.post-32896531038795529132013-09-06T09:58:10.081-04:002013-09-06T09:58:10.081-04:00Process Chemistry is not always that simple as in ...Process Chemistry is not always that simple as in most cases it is likely best to maximize at reaction stage to minimize purification requirements there are times that secondary impurities that are difficult to remove if run too long so may halt before achieving full conversion. Comes back to understanding the mechanisms and by-products involved, which sometimes early on is more guess work or semi-empirical that complete knowledge. If have a inexpensive reagent that is easy to remove, say by extraction or wash, then may employ excess to push to the right side. When one knows what crystallization or other methods can handle or not handle certain impurities will influence details of operations. Unlike medchem in process chem the reaction and purification are approached more as a package to balance out because typically do not have realistic chromo options (and purity profile demands less critical)Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8964719845369935777.post-89133226471902595682013-09-06T04:13:28.067-04:002013-09-06T04:13:28.067-04:00I was also wondering about that issue. Lower conve...I was also wondering about that issue. Lower conversion means more impurities being present, means a more troublesome workup/purification procedure. Tantalnoreply@blogger.comtag:blogger.com,1999:blog-8964719845369935777.post-30463469627957760762013-09-05T23:28:28.863-04:002013-09-05T23:28:28.863-04:00I thought that part of the reason to optimize yiel...I thought that part of the reason to optimize yield is to minimize purification - for example, in recrystallization, impurities prevent some of the desired product from crystallizing and so for every bit of impurity or starting material left, you lose some of your product. You also have to go through more manipulations presumably to get the desired material out. Is this at the stage when the workup and purification steps are consistent enough or known enough to make good correlations between yield in situ and isolated product, or is this a legitimate issue?Hapnoreply@blogger.comtag:blogger.com,1999:blog-8964719845369935777.post-48855225956271896712013-09-05T22:37:00.512-04:002013-09-05T22:37:00.512-04:00This time vs yield analysis is also critical in ea...This time vs yield analysis is also critical in early stage discovery.Dr. Zoidbergnoreply@blogger.comtag:blogger.com,1999:blog-8964719845369935777.post-63270686686560442542013-09-04T16:22:38.750-04:002013-09-04T16:22:38.750-04:00I love Process Wednesday. I always learn something...I love Process Wednesday. I always learn something interesting. :)Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8964719845369935777.post-26180011053040712252013-09-04T11:24:49.749-04:002013-09-04T11:24:49.749-04:00You may be correct that appreciation of variable c...You may be correct that appreciation of variable costs in more ingrained in chemists, partly because in grad school rarely is the people time a concern and overhead nebulous factor taken out of grants. However this is at the core of most ChemE training that hopefully can be used to educate process chemists. Although management may not want to divulge burden rates externally all plants I dealt with had defined cost per day and we always worked to reduce time because often had the biggest impact of production costs. Activity does take longer in the plant naturally however the more one studies and know the process can often find ways to shorten. No more customary overnight or 72 hours reaction times allowed without proof.Anonymousnoreply@blogger.com