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Author: Subject: questions about synthesis

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[*] posted on 7-4-2012 at 11:46
questions about synthesis

What causes, in a chemical reactions the different things to bond, I am thinking that it would be electromagnetivity and valency and ease to bond. But what else is there? And how can I, on my own predicty what will happen.
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International Hazard

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[*] posted on 7-4-2012 at 12:21

You have the main basics covered, electronegativity being the main one that influences whether the bond will be ionic, covalent etc. Ease of bonding relates often to individual atoms and their layout, and valency can be a big part of this. Another one that determines what bonds will happen and how quickly is activation energy and reagent stoichiometry. For example, under an inert atmosphere, with an appropriate amount of oxidizing agent a primary alcohol will only be oxidised to the aldehyde, and it will not proceed to form the carboxylic acid - again, the bonds that form depend on what is thrown into the reaction pot and under what conditions.

You can often predict what will happen in chemistry by looking at the properties of your starting and ending materials and determining, if, under conditions X, event Y will actually take place. Another way is to look for reaction patterns, such as Grignards, Wittigs or Haloform reactions, and seeing if your reagents conform to the 'rules' of such reactions.

[Edited on 7-4-2012 by Hexavalent]

"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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[*] posted on 7-4-2012 at 13:44

A lot of inorganic reactions can be predicted on a basis of solubility. Consider the following equilibrium established when calcium nitrate and sulfuric acid are mixed:

Ca(NO3)2 + (NH4)2SO4 <----> 2NH4NO3 + CaSO4

CaSO4 has poor solubility in water and precipitates as a solid, driving the reaction to the right by taking one of the products out of the solution.

Consider HCl reacting with Na2CO3:

HCl + Na2CO3 ----> NaCl + CO2 + H2O

Again, this reaction is driven by the loss of a product. Note how the CO2 leaves as a gas and drives the reaction to the right.

A similar thing can be done with distillation:

2NaCl + H2SO4 <---> Na2SO4 + 2HCl

By heating this equilibrium, the HCl (the most volatile component) evaporates out, forcing the reaction to proceed to the right.

Victor Grignard is a methylated spirit.
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