# deduce chemical properties of a compound from elements

If we know the properties of two elements e.g Oxygen and Hydrogen.

We know the following properties

• sound speed
• boiling point
• melting point
• refractive index
• etc.

given that information, is it possible to deduce the properties of a compound such as water H2O without resorting to chemical experiments? i.e deduce its boiling point

• You're not being very clear here... Do you want to deduce physical or chemical properties? You asked for boiling point, that is a physical property. (Aside from asserting that we already know it) – ManishEarth Sep 2 '12 at 12:57

is it possible to deduce the properties of a compound such as water H2O without resorting to chemical experiments?

Not yet, assuming you mean extrapolating such information from the molecule's structure

Physical and chemical properties are hard enough to extrapolate from a compound's structure, let along its composition. The entire field of theoretical chemistry has been working on predicting the structure-property relationship for several decades. Great strides have been made, but accurate physical property prediction has not been achieved (though I would love to be proven wrong). In most cases, very accurate computation of properties of all but the smallest molecules takes more computing time than you would need to do the experiment.

Your question implies an interest in deriving such properties from the formula. As Canageek said, this is not possible, given the phenomenon of isomerism. One example I just used with my class is that there are 22 known molecules sharing the formula $\ce{C6H12}$, which is a relatively simple formula. Two of the more common are1-hexene and cyclohexane, which you can see have very different structures and properties (chemical and physical).

• I had a friend do his undergraduate thesis on this, and he wasn't able to find any trends within the physical property database he was working on. Best was a R^2 of .7 or something, with a ton of visible jitter in the data. – Canageek Sep 3 '12 at 4:47

No. Calculating the physical properties of materials is very, very difficult and can't simply be done from the elemental composition.

• it will also depend on Geometry of molecule, polarity and Crystals. – BigSack Sep 2 '12 at 13:44
• Even knowing that the compound is made out of hydrogen and oxygen is not good enough, since there are two well known binary compounds of hydrogen and oxygen, each with different properties: $\ce{H2O}$ and $\ce{H2O2}$. – Ben Norris Sep 2 '12 at 16:09