It is important to know what exactly happened and what exactly they used. Depending on the reaction mechanism, water could easily form. Or did they use a hydrate as precursor? Also the solvent could contain water even though it is "dried". It is a challenge to remove water from acetonitrile for example. Anyway: Drying means to reduce the level of water to a certain ppm value.

It would be nice to know how they dried their solvents. I met someone who claimed that he dried the solvent by bubbling argon through it for 10 min. That removes air but certainly not water. How did they dry which solvent? For acetonitrile it certainly does not suffice to let it run through activated Al2O3 but you need to reflux it over P2O5 and then distill. For dichloromethane however activated Al2O3 suffices.

Thus the probable causes are:

- precursors

- solvents (still)

- reaction mechanism

Ahmed,

I will call it from the reaction medium if it comes out of the reaction, or the solvent of crystallization they used to recrystallize the product. As Evers mentioned above it depends on how do you dry the solvent [to what specific level] and how do you perform the reaction [e.g. handling the reaction under inert atmosphere and/or in a dry box..etc].

Good luck

Very often the crystallisation water is contained in salts as chloride, sulfate, phosphate, of alkaloids. The water content is even due to the procedure. e.g. if you want to prepare the chloride of an alkaloid you could bubble gaseous HCl in a ethereal solution of the alkaloid and the easier way to generate HCl is to react NaCl and conc.H2SO4. The reaction is exotermic and the water contained in the conc. acid will vaporize and bubble together with HCl in the alkaloid solution.

In order to make a hypothesis is necessary to know exactly the procedure followed in that article.

It is unusual in organic synthesis to report water of crystallisation as a standard course of action unless it was for the purposes of X-ray crystallography. In general if crystals have been grown for the purposes of crystallography then the solvents used to grow that crystal are not given. Depending on the method of crystallisation the source of water is most likely atmospheric.

I worked long time ago on lauraldehyd, this compound is a liquid but forms an solid hemihydrate very easily. When I opened a one liter bottle of liquid laurald bought from cosmetic industry, the entire bottle turn immediately to solid. Such very hygroscopic compound can get an impressive amount of water from short exposure to atmospher, also it supports the view of Eric (water from atmospher).

As you know, in hydrates of inorganic compounds (which contain H2O in definite ratios e.g. the blue CuSO4.5H2O), the water of hydration or crystallization is part of the crystals themselves.

In a similar way to the inorganic salt hydrates, a number of organic compounds have water of crystallization within their crystalline structure. An example is the sugar trehalose (also known as mycose or tremalose) which has the anhydrous form & the dehydrate form (i.e. for each molecule of trehalose, there are 2 molecules of water i.e. its formula is C12H22O11.2H2O). The presence of water of crystallization affects physical properties (e,g. color, melting point…) but it has no considerable effect on the chemical properties.

So it is reaonable that the researchers have dried the solvents but obtained an organic compound with water of crystallization.