When we carry out reactions there may be further reactions involved in the solvent, in other words it may react as a reactant. How can I predict this or how to avoid this?
With taking sample and analysing solvent concentration you can evaluted solvent quantity and if the quantity of it was decrease it shows that it will react as a reactant.
According reaction situation and type if it is possible you can avoid solvent to be as a reactant.
Regards
It is in general a very knotty problem for a simple answer. Pleas, specify a reaction according to a character of other reagents, i. e. starting substrate is electrophile and reagents are nucleophilic = nucleophilic reaction condition, or radical reaction condition, ...
It is a good question Mohamed, I think every researcher must understand this concept before starting reaction. But in order to choose your right solvent, it is very important to know what type of reaction it is and possible mechanism as well. For example you can not choose any polar protic solvents such as Methanol, Ethanol or iPropanol in many Nucleophilic substitution reactions because they themselves are good nucleophiles hence your actual nucleophile would hardly react. That is the reason why we use anhydrous solvents in this type of reactions to avoid H2O molecule to act as nucleophiles. Additionally, DMF or DMSO are best solvent for the reaction where both organic and inorganic reagents are used. Meanwhile, they are avoided where you use acid chloride, SOCl2 or oxalyl chlorides since they tend to form Vilsmeyer-Haack Reagent in situ. Generally, we must understand the complete reaction mechanism of what we do. All the best.
Generally there are few surprises if you understand the possible mechanisms that can occur with the given reaction mixture. C-H activation during transition metal-containing reactions would be the one real exception-that one always catches me off guard. As everyone else very wisely points out, it is completely dependent on what exactly you are doing. Generally etheric and chlorinated solvents (or hydrocarbon-solvents to an even greater degree) are the least reactive, although there are definitely cases where one class or another would be an unwise choice. THF can often be a safe choice for the vast majority of conditions (although caution must be taken with substituted butyl lithiums and very strong acid).
You can change the solvent to another one in wich you know there is no reaction between solvent and substances and prepare your solutions, then add a small quantity of the solvet you think is reacting and compare.
The reaction of solvent with substrate depends on its polarity and the nature of a substrate, e.g. methanol or other alcohol may participate in reaction with carbonyl group of aldehydes or ketones if present in a substrate forming semi- acetals, acetals or ketals. Also the pH plays a key role, wether reaction occurres, or not. At pH higher than 7, a nucleofile reaction may takes place.The rate of reaction depends on temperature, sterical hindrance of functional group in a substrate and on polarity of
R-O-H goup in alcohol /primary, secondary or tercial one/.
This was only an example.
It is always useful to consider the presence of reactive functional groups or sites /structures/ in the substrate, that might undergo to nucleophilic or electrophlic attack by molecules of the applied solvent. The radicial interactions between substrate and solvent could proceed mostly under very severe reaction conditions, or in the presence of reactive impurities or iniciators of radical polymerisations.
The best way how to avoid undesired ractions between solvent and substrate is to know the purity and properties of the both used moieties.
Generally suitable solvents for non polar substrates might be, tetrahydrofurane, benzene, xylene, or higher alkanes or their chlorinated /florinated derivatives. In the case of polar substrates a suitable solvents might be anhydrous alcohols or their acetylesters, ethers and sometimes pyridine /its pH however, is alkaline/. In other special cases even liquid ammonia could be used, etc.
The reaction between two or more reactants depends on their solubility in the solvent employed for the reaction.If you can carry out the reaction in two different solvents having equivalent solubility and compare the kinetics in the two different cases.In case the kintics is similar, the solvents are not participating, but if there is significant difference in the kinetics, the solvent 's participation is clear.
It depends upon the reaction mechanism for choosing an appropriate solvent for a chemical reaction. All solvents can't be used for all type of reactions. So you have to choose the right solvent( polar/non-polar) for a particular reaction keeping in view to the nature of the reactant. For other examples please follow Nagarajan's post.
You must consider that there are not general inert solvents. Solvents are organic molecules like your substrates and you can also consider them as reactants. There are solvent that can seem "inert" to the kind of reaction you are doing or to the conditions of reaction you have selected but usually solvents are not mere spectators, they stabilize intermediates, or help to start or finish steps of the reaction. Even when you plan a reaction thinking of the reactants alone, you should know that the mechanism of reaction greatly depends on the solvent.
Obviously I don´t want to talk about solvent incompatibilities
If you have a subtrate that you want to react to produce a product always think in possible mechanisms of that reaction and after that what reagents you have to add and solvent you must use to make the reaction go well.
Obviously I don´t want to talk about solvent incompatibilities, this topic is rather clear just on reading MSDS of each compound (solvents are also compounds). I don´t consider necessary to warn anyone about the danger of organic chemistry in inexperienced hands.
Hi,
Participation of solvent in reaction can be observed by writing the plausible mechanism for product formation involving the solvent and then the presence of expected product should be checked by using NMR.
In order to avoid this either take very large amount of solvent or use other solvent with the same property but less or no chemical reactivity.
Solvent is usually used for dissolution or extraction of some substance under various physical and chemical conditions.Solute may contain different chemical / physical properties that can be simple or complex. Thus one can predict/find structure/properties of new product by simple method normally used in synthesis processes such as chemical or plant origin.
If the solvent selected and reactant interact forming a new undesired product/s/, not addition compounds, and there is at the hand a *GLC or HPLC, make just a simple test: compare chromatigrams of both chemicals prior to their mixing with that from a mixture of the solvent and reactant /It is recomended to allow the mixture some time to react, if there is suspection of occurrance of chemical reaction. Sometimes you can find satisfactory data in the special guides or calendars provided customers by companies producing special, and extra pure chemicals, e.g. Merck...../
See one important reference.
http://www.nature.com/nchem/journal/v5/n11/full/nchem.1755.html?WT.ec_id=NCHEM-201311
Solvent for any reaction is selected so that it does'nt have a functionalty which can possibly react with reactants.If a reactant "A" is dissolved in a solvent , the solvent molecules usually form an envelope around the molecule of "A" (Solvation number).If reactant "B" has to react with "A" it has to displace the solvent molecules, meaning thereby that B should have more affinity for A than the solvent.If this condition is not fulfilled, there is no resultant reaction.
From a theoretic/computational standpoint and by QM methods, one can simulate the possible reactions which may occur at the desired reaction centre between the latter and a number of different solvent molecules. The reaction parameters (DeltaG and and DeltaG of activation) between the centre of interest and the other reactant can be used as a reference point. Thus if the reaction parameters associated with the reaction between the centre of interest and one type (or more types) of solvent molecule are less favoured than those associated with the reference point, one can have an initial hint about the thermodynamic and/or kinetic propensity of the solvent to compete with the other reactant for the reaction centre. Of course, if the opposite holds true, the solvent should be to consider as "non innocent" or "coordinating" or non inert, according to which kind of chemical reaction one has been investigating.
Это очень просто! Надо знать химические свойства веществ - растворителя и растворимого вещества!
If the solvent is water run a CV-- Uni molar is also possible
if the solvent is non polar, change the solvent and see the final product-- try diffent solvent mixtures and follow the kinetics
let me come back later with more knowledge
Do you mean Theoretical Calculations? I would say a combined Polarizable Continuum method altogether with discrete molecules of solvents. The firts step to take is Molecular dynamics (Delta G) and then QM (electronic).
A GUESS
Change the solvent and follow the kinetics- follow reaction order
if the final product is different then your solvent had participated
Purpose of solvent is to dissolve/extraction. With the help of paper chromatography technique select such solvent which should not reactant. If solvent react some complex compound will formed during the chemical synthesis which may differ to hypotheses/ desired compound.
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