- characteristics
- Structure
- Examples of compounds with isopropyl
- Isopropyl alcohol
- Isopropyl Halides
- Isopropylamine
- Lorcainida
- Others
- References
The isopropyl or isopropyl is an alkyl group or substituent, one of the most common and simple found in organic chemistry. It is one of the structural isomers of propyl, CH 3 CH 2 CH 2 -, a group derived from propane, CH 3 CH 2 CH 3. Its skeleton could be written as (CH 3) 2 CH-, showing that it also has three carbons.
Isopropyl when found in large molecules is simplified with the symbol iPr; although in small compounds it is not necessary and it is very easy to identify it. A variety of organic compounds can be obtained from it which, although simple in appearance, are versatile for different applications; including isopropyl alcohol, (CH 3) 2 CHOH.
Isopropyl group skeleton. Source: Wostr
Shown above is the carbon skeleton of the isopropyl group. Note that in the center we have the “secondary” carbon, which is linked to two methyl groups, CH 3, a hydrogen and an unknown segment represented by sinuosities; These can be a heteroatom, functional group, aliphatic chain (R), aromatic ring (Ar), etc.
If observed, the isopropyl group resembles a Y, a characteristic that is essential to recognize it at first glance when considering any molecular structure. The smaller isopropyl is compared to the molecule of which it is a part, it is said that it acts simply as a substituent, which is the case in many compounds.
characteristics
Involving a little more the chemical nature of the isopropyl group, we can add that in addition to being alkyl (and aliphatic), that is, composed only of carbon and hydrogen atoms, it is nonpolar. This is because all of its bonds, CH and CC, are low polarity, so there are no electron-rich or electron-poor regions (dipoles).
The apolarity of isopropyl does not mean that it is poor in electrons; on the contrary, as a substituent it gives them to the more electronegative atoms. That is why wherever we see the Y in a molecule, we will know that it has given electronic density to its surroundings; although the end result is to be a zone lacking a dipole.
Isopropyl is also said to be aliphatic because it lacks aromaticity, found in rings with conjugated double bonds (benzene type).
Regarding its name, the origin of the iso- prefix will be explained in the next section. However, its IUPAC name comes to be 1-methylethyl, since in the second carbon of the ethyl chain, -CH 2 CH 3, we substitute an H for a methyl group, -CH (CH 3) CH 3, which can also be written as -CH (CH 3) 2.
Structure
Structure of the isopropyl group. Source: Gabriel Bolívar via Mol View.
The structure of the isopropyl group is shown above, represented by a sphere and bar model. In it we again appreciate the Y; but it is not flat as one might think at first. The white box acts like the sinuosities in the first image, hiding the other segment of the molecule regardless of the compound.
All carbon atoms have sp 3 chemical hybridization, so it is not possible for them to reside in the same plane. The CC links have an approximate angle of 109.5º, which deforms the ends of the Y a little below or above its hypothetical plane.
This perspective on its structure is very useful because it makes it even easier to recognize when looking at other molecular models.
If a plane serving as a mirror were drawn in the middle of the CH carbon, it would be seen that the methyl groups are "reflected" on both sides of the mirror. Therefore, this plane divides the group -CH (CH 3) 2 into two identical halves; a fact that would not happen with propyl, as it is straight chain. Hence comes the prefix iso-, for 'equal', used for this alkyl substituent.
Examples of compounds with isopropyl
Isopropyl alcohol
Perhaps isopropyl alcohol is the most notable isopropyl derivative compound, since it is also the simplest secondary alcohol, widely marketed in plastic bottles in pharmacies as an antiseptic solution. Its structure is:
Molecular structure of isopropyl alcohol. Source: Jynto
Note that in the center, under the OH group (red) we find the Y again, giving the false appearance of being flat. This alcohol is obtained simply by changing the sinuosities or the white box already shown by the OH group. The same applies for other groups or heteroatoms.
Isopropyl Halides
Suppose now it is not the OH but a halogen atom X (F, Cl, Br and I). In that case, we get the isopropyl halides, XCH (CH 3) 2. These organic compounds are characterized by being highly volatile liquids, possibly used as isopropyl sources in alkylation reactions (their addition to other molecules).
Among these halides therefore we have:
-Isopropyl fluoride, FCH (CH 3) 2
-Isopropyl chloride, ClCH (CH 3) 2
-Isopropyl bromide, BrCH (CH 3) 2
-Isopropyl iodide, ICH (CH 3) 2
Their structures are identical to that of isopropyl alcohol, only changing the size of the atoms attached to the central or secondary carbon.
Isopropylamine
Molecular structure of isopropylamine. Source: Jynto
Now it is not the OH or the halogens, but the amino functional group, NH 2 (upper image). As with isopropyl alcohol, isopropylamine is a secondary amine and a starting point for the synthesis of various insecticides. It is not marketed in the same way, since it is stinky and flammable, therefore being a dangerous compound.
Lorcainida
Structural formula of lorcainide. Source: Fvasconcellos
We left behind the derivatives of isopropyl and began to see it as a simple substituent. Lorcainide (above) is a controversial drug used to normalize heart rhythms. If you look at the molecule, it will be easy in a few seconds to see the Y on its left, which represents isopropyl.
In some formulas, the symbol iPr is used instead of Y; but it is usually applied for even more voluminous and complicated molecules.
Others
Finally, other examples with their respective formulas or structural models will be cited to serve as an exercise to locate isopropyl:
Formula or chemical structure of mazapertin. Source: Ed (Edgar181)
The Y for isopropyl is now located on the right side according to this representation of the antipsychotic drug mazapertine.
Structure of trisopropylphosphine. Source: Smokefoot
This time we have three isopropyl groups, P (CH (CH 3) 2) 3, represented by three Y's. The formula could also be written as PiPr 3 or P (iPr) 3.
Molecular structure of thujine. Source: Edgar181
And finally we have the monoterpene thuyen, whose structure at first glance can cause confusion as to where the isopropyl is found. But after looking at it calmly, you will notice that it is at the top.
References
- Morrison, RT and Boyd, R, N. (1987). Organic Chemistry. 5th Edition. Editorial Addison-Wesley Interamericana.
- Carey F. (2008). Organic Chemistry. (Sixth edition). Mc Graw Hill.
- Graham Solomons TW, Craig B. Fryhle. (2011). Organic Chemistry. Amines. (10th edition.). Wiley Plus.
- Steven A. Hardinger. (2017). Illustrated Glossary of Organic Chemistry: Isopropyl. Recovered from: chem.ucla.edu
- Elsevier BV (2019). Isopropyl Group. ScienceDirect. Recovered from: sciencedirect.com
- Wikipedia. (2019). Category: Isopropyl compounds. Recovered from: en.wikipedia.org