Can, and if so, how do chemists predict the physical characteristics of a chemical reaction that they don’t already know the byproduct of?

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Do they just have an idea of how something will react generally, like knowing something will combust or change color, etc, or can they also predict the degree to which it will occur based on their understanding of the reaction itself? Is there just a lot of speculation?

In: Chemistry

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Organic chemistry is based on the understanding of function groups and how they react with one another. We can look at molecules and make educated guesses about how molecules will react with each other based on their electronics based on all the functional groups on the molecule and how the molecule is bound together. Also we take into account the shape of the molecule, as even in molecules, parts can block access to these functional groups.

Also, there are many well known reactions called name reactions. They’re usually named after the chemists that published them. They are reactions between specific functional groups that produced a known result. I can make an educated guess if it will work with my molecule, but the only way to really know is to try it and analyze the results.

When we work, we usually just care about what molecules come out. Color can sometimes be guessed based on certain functional groups and other structures, but we usually don’t care about it. Most pure chemicals are white powders.

Combustion is usually not a good thing for me so I try to avoid it.

In a simple sense, the periodic table of elements is a table that organizes all elements into rows and columns based or characteristics. Each element is made up of subatomic particles called protons, neutrons and electrons, in a relatively intuitive and predictable pattern. As you go along the table from left to right and top to bottom, each subsequent element gains 1 of each subatomic particles. (This is not close to accurate since there are many, what are called isotopes which have varying amounts of neutrons. The element number is based on the number of protons, but it works here in the simplistic sense.) The most commonly used example is the last column, which is called “Noble gasses”. This is a group of inert gasses. How do we know they are all inert though? because they have full outer ring of electrons and therefore cannot react with other elements.

The electrons are the main driving force for reactions. depending on how many are in the outer shell will determine whether an atom wants to donate or steal and in some cases share electrons. So, for instance in our case of Noble Gasses, since their outer shell is full, they neither want to take nor give since it wont benefit them. This all ties into another concept called electro-negativity which determines the relative strength of each atom and can predict which will “win” in a molecule.

This all just gets more complex as you go. There are ways to measure and predict the outcome of many factors in a reaction such as pH, the molecule itself, the type of structure it will have etc. If there are any particular points you want more explanation on, let me know.

tl;dr: Chemistry is a complex science and they can predict fairly accurately beforehand what the results will be.