suggestions for a simple chemical reaction

Lets say I have an analytical technique that can determine % of products and reactants in a mixture, but I only have a balance to confirm the accuracy of that technique.

I’m looking for a simple, inexpensive, safe, common(?) chemical reaction that allows me to test this technique and confirm it with my balance.

One possibility: I’m thinking of a reaction, where the reactant is easily dissolved but the product isn’t. So I can weigh the mixture, dissolve out the reactant and reweigh the dried product.

It probably should be an organic reaction, and the easier it is to handle and dry the better

Ideas chemical dopers?

Oh and if you happen to be a chemist type where you have mixtures you are trying to analyze let me know through here or a private message. I’d be happy to try it out.

Organic reactions where the product precipitates out are rare unless you are talking about a polymerization. Worse yet, most organic reactions are far from quantitative and the ones that are require some skill. An easy reaction to do that results in a precipitated product is the hydrolysis of a large ester. You simply reflux the ester in methanol with xs KOH. But the product doesn’t precipitate out until you work it up. Work up varies from one setg of conditions to another, but ordinarily I would reduce the methanol volume by evaporation. Then I would add ether and wash with aqueous base. The acid product will wash into the aqueous layer. When you acidify the aqueous layer with hydrochloric acid the acid will precipitate out.

Of course every acid will behave differently even with minor changes. You don’t want an ester that is too big or it will form an emulsion rather than extract into the aqueous layer. If it is too small, it will not form a solid. Ethyl benzoate might be a good choice.

More complicateed reactions could work as well. Getting a product to precipitate directly out of an organic solvent is tough. Really large flat molecules will precipitate out. You might be able to use a vinyl anthracene then add in Grubbs catalyst. You will lose ethylene and the resulting product is probably large enough to that it could have major solubility problems. The reaction is extremely simple to do and usually is very quick. You essentially only have one starting material. Grubbs catalyst is incredibly efficient so you don’t need much of that (good thing too since it’s pricey).

For that reaction you would want to use a relativily non-polar and non-aromatic solvent in order to encourage the product to precipitate out. If you can get the starting materials into hexane, I’d go with that. One problem is that you will have two isomeric products that may have different solubility issues.

Inorganic reactions that meet your are much more common. Sulfuric acid and barium chloride are both very soluble in water, but their product barium sulfate is very insoluble.

The truth is, I’m not sure why you want to do a reaction to test your method. Reactions have variable outcomes. If you are checking an analytical method, it makes more sense to weigh out your own standard. Why do a reaction that adds the uncertainty of yield?

This is the usual chem 109 reaction:
“steel wool” stoichiometry

I can do the mixing of chemicals and perform the analysis on the mixture. I want to move to a more complicated error prone test…A “real world” set of samples.

I not really thinking so much of a reaction that produces a precipitate. I’m more thinking of mixtures of solids, or liquids, or even slurries perhaps that I can easily find the actual concentrations of at least one of the components. But I really only have a balance right now to do analysis (no HPLC, no GC, I don’t even have a buret for titrations, but I might be able to “wing it”)

So I can MAKE mixtures of solids and liquids and slurries; but what I really want is a chemical reaction that results in said mixtures. Determining the actual concentrations of the mixtures with my limited tools is not easy.

Hence my question of some simple chemical reaction that will allow that

I knew I shouda put “sex” or “naked” in the title

If a messy real world reaction is what you want you could go with the solventless Aldol condensation of 3,4-Dimethoxybenzaldehyde and 1-indanone. Just crush them together and add a tiny bit of NaOH. It’s a goo.

You will not get a good yield, but you said you wanted a real world situation and that’s the real world.

Could I then find the amount of product produced by dissolving away the dimethoxybenzaldehyde and 1-indanone?
What would I use to remove the product from the reactants to get an idea of the mass of the product (or mass of remaining reactants would work too)

I think the only prayer you have of doing that is by recrystalizing and that takes major experience to get get right. Even when you are good, you will likely lose 10 - 20% of your product. For this reaction, you want to recrystalize by dissolving it in hot ethanol then dropwise adding water until it just starts to look cloudy when you add it, then clears. Then you let it cool slowly. Then you put it in ice. Then you vacuum filter it.

The alternative is to run a column, but since you don’t know how to separate your products in the first place you don’t know how to run a column. You still lose product. Sometimes your reactants are too close your products to separate this way.

There is almost never a solvent that dissolves all of your reactants and leaves your product. The hydrolysis I mentioned first comes closest to achieving this, because when you acidify the basic aqueous layer, your product drops out. All you have to do is dry it and weigh it.

Some reactions are easy to set up, some aren’t. Almost all of them require skill to separate your products.