Suggestions for future customers
Being a grey haired chemist in the manufacturing field, allow me to make a few suggestions regarding the design of custom chemicals. If you as a customer would like to have a custom product that has minimal cost, maximum quality, and minimum variability, please consider the following attributes of an ideal custom synthetic chemical product.
Boundary conditions must be set on my comments: custom or proprietary product; produced under batch or semi-batch conditions; non-pharma-food-neutriceutical related.
To the greatest extent possible the raw materials for your product are preferably-
- existing items of commerce unencumbered by composition of matter or process claims.
- available in a grade suitable for direct use.
- unencumbered by import restrictions, law enforcement watch lists, and relevant EPA restriction lists.
- TSCA and REACH listed already.
- those free of problematic isomers.
- those not requiring tight fractional distillation to purify.
- free of explosaphors like azide or nitro esters.
Your costs are best contained if your product-
- does not require enantiomeric purity or is not subject to facile isomerism affecting the specification.
- does not require more than one protection/deprotection scheme.
- does not require tight fractional distillation for final purity.
- does not require bulk high pressure chemistry (shops that can do this are limited).
- is air stable.
- is soluble enough in process solvents to maximize space yields (if it is, say, <10 wt %, batch costs will start to get high).
- does not require solvent changes in a process unit operation.
- is amenable to parallel synthetic strategy.
- does not require serious chilling of the reaction mixture (say, < -20 C).
- has been screened for real purity requirements rather than those based on the desire for tidiness.
- can be isolated by a simple Buchner filtration rather than, say, a centrifuge or other more elaborate solids isolation scheme.
- can be isolated by simple distillation.
It is important not to underestimate the cost of excess purity. A process may afford 96 % absolute purity on first isolation with say, 1 % solvent and 3.5 % side products or starting materials. The cost of taking this to >99.5 % is often very high in plant time and in product losses from added operations. Maybe you can get by with 98.5 % purity with some constraints on certain contaminants for your application.
Products and their intermediates may be designed in the early development stage to have properties that aid in low cost manufacturing without too much alteration of utility. For example, consider not using an n-octyl ester group in favor of 2-ethylhexyl ester. There are many structural motifs that derive from large scale items of commerce. Products that are strictly polyaromatic with or without hetreroatoms, are zwitterions or salts, or have a large heteroatom-to-carbon ratio, often have organic solubility problems. Will a bit of aliphatic shrubbery in a side group enhance processability? Maybe. If it allows your vendor to have better process economics, that helps everyone.
Does the process require nitromethane as a solvent? Does it require an exotic PGM catalyst that is patented? Do you have to use a patented transformation in the scheme that requires pencil-necks from the University IP office to audit annually? If so, try to find a better way.