The isobutyl or isobutyl is a radical or alkyl group that originates from the alkane isobutane, one of the structural isomers of butane, C4H10. Thus, isobutyl integrates the butyl groups, the others being butyl, tert-butyl and sec-butyl. Its structural formula is -CHtwoCH (CH3)two.
The bottom image illustrates the isobutyl or isobutyl group. R is a side chain, which can be any carbon skeleton that, given the definition, is aliphatic and therefore lacks aromatic rings. R, likewise, can represent the rest of the molecular structure of a given compound, with isobutyl just a segment of said structure..
The isobutyl group is easy to identify in structural formulas because it resembles a Y.
When this Y encompasses a large part of the structure, the compound is said to be an isobutyl derivative; while in the cases in which this Y looks small compared to the rest of the structure, it is then said that the isobutyl is nothing more than an alkyl substituent.
Isobutyl alcohol, (CH3)twoCHCHtwoOH, with a higher molecular mass but with properties different from those of isopropyl alcohol, (CH3)twoCHOH, is an example of a compound where the isobutyl segment makes up almost the entire molecular structure.
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This group is known much more by its common name, 'isobutyl', than by the IUPAC nomenclature name, '2-methylpropyl'. The latter, less used, is more faithful to the fact that isobutyl is derived from isobutane (upper image).
Note that isobutane has four carbons, three of which are terminal; These are the carbons numbered 1, 3, and 4 (the CH3). If one of these three carbons lost any of its hydrogens (in red circles), the isobutyl or 2-methylpropyl radical would be formed, which would bind to an R side chain to become an isobutyl group or substituent.
Note that the result is independent of the hydrogen removed. They do not necessarily have to be those that are enclosed in the red circles, as long as it is not those of carbon 2, in which scenario it would give rise to another butyl substituent: tertbutyl or tertbutyl.
Isobutyl is an alkyl substituent, so it lacks unsaturations, and is composed only of C-C and C-H bonds. Its common name is due in the first instance to the fact that it derives from isobutane, which in turn is known as such because it has a symmetric structure; that is, it is the same no matter how you look at it or rotate.
Isobutyl is also symmetric, since if it is divided into two halves, one will be the "reflection" of the other. This group, like the other alkyl substituents, is hydrophobic and nonpolar, so its presence in a compound suggests that its character will not be too polar..
In addition to these characteristics, it is a relatively bulky and branched group, especially when all its hydrogen atoms are considered. This affects the efficiency of intermolecular interactions. The more of these groups there are in a compound, it is possible to infer that its melting and boiling points are lower..
On the other hand, its higher molecular mass compared to the isopropyl group, contributes to London's dispersive forces. This is the case, for example, of the boiling points of isopropyl (82.5 ° C) and isobutyl (108 ° C) alcohols.
Compounds derived from isobutyl are obtained when in the formula RCHtwoCH (CH3)two R is substituted for any heteroatom or organic functional group. On the other hand, if this is not enough to describe the structure of a compound, then it means that the isobutyl behaves only as a substituent..
Isobutyl halides are obtained when R is replaced by a halogen atom. Thus, for fluorine, chlorine, bromine and iodide, we will have isobutyl fluoride, FCH, respectively.twoCH (CH3)two, isobutyl chloride, ClCHtwoCH (CH3)two, isobutyl bromide, BrCHtwoCH (CH3)two, and isobutyl iodide, ICHtwoCH (CH3)two.
Of all of them, the most common is ClCHtwoCH (CH3)two, which is a chlorinated solvent.
Mention was made earlier of isobutyl alcohol, (CH3)twoCHCHtwoOH. Now, if instead of the OH group we have the NH grouptwo, then the compound will be isobutylamine, (CH3)twoCHCHtwoNHtwo (top image).
Note how the Y of isobutyl covers almost the entire structure, NH beingtwo the substituent and not the isobutyl itself. However, in most compounds where it is found in isobutyl, it occurs as a substituent.
Similar to the case of isobutylamine, if instead of NHtwo outside the GeH group3, then we would have the German isobutyl, (CH3)twoCHCHtwoGeH3.
In the image above we have the formula for isovaleric acid. Note how isobutyl is easily recognized by the four-carbon Y attached to the carboxyl group, COtwoH or COOH, giving rise to this acid, (CH3)twoCHCHtwoCOOH.
In both the previous example and this one, isobutyl begins to take a back seat of importance due to the oxygenated groups with which it is linked. Now we have isobutyl acetate (above), an ester found in nature as part of the natural essence of pears and raspberries, and which is also a very recurring organic solvent in laboratories..
Hitherto the examples cited have consisted of solvents or liquid substances. The next two will therefore be solid and consist of drugs.
In nisoldipine, a drug that lowers blood pressure, isobutyl is seen as a simple substituent (top image). Note that it is now just a molecular fragment of a much larger structure.
In carfilzomib, a drug used to combat multiple myeloma, isobutyl has even less structural relevance (top image). Note that it is easily and directly identified by the presence of two Y's on the left side of the structure. Here again, isobutyl is just a fraction of the molecular structure..
As in the examples of nisoldipine and carfilzomib, there are other drugs and compounds where isobutyl, as usual, only appears as a substituent alkyl group..
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