Properties of Iso Compounds
We use the prefix iso to identify an organic compound that has all carbon atoms, except one, arranged in a continuous chain. So, we use this phrase whenever a molecule has a single branch. The carbon chain splits off at this point.
The term "iso" can also refer to a molecule that is a constitutional isomer of another molecule having a common (or trivial) name.
Structure and Bonding of Iso Compounds
Iso is a prefix that describes an organic molecule with all carbon atoms except one that forms a continuous chain. As a result, we use this phrase when there is just one branch in the molecule. This branch is found at the very end of the carbon chain.
This branch is known as the "terminal isopropyl group." When a methyl group is connected to the second carbon of a carbon chain, we use the prefix iso to designate the molecule. Isopropyl alcohol, for example. This prefix can identify compounds with at least four carbon atoms.
Two crystals are considered to be isostructural if they have the same structure but not necessarily the same cell v or chemical composition and if the variability in the atomic coordinates is 'similar' to the variability in the cell dimensions and chemical composition. Calcite CaCO3, sodium nitrate NaNO3, and iron borate FeBO3 are all isostructural. Isostructural series, polymorphs, and phase transitions are other terms for the same thing. The terms isotypic and isostructural are interchangeable.
Nomenclature of Iso Compounds
Some branched alkanes have popular names that are still used today. Prefixes such as iso-, sec-, tert-, and neo- are used in these common names. 2-methyl alkanes are usually prefixed with the word iso-, which stands for isomer. In other words, if a methyl group is found on the second carbon in a carbon chain, the prefix iso- might be used. The prefix shows the total number of carbons and will be placed before the alkane name.
Examples: Isopentane is the same as 2-methylbutane, whereas isobutane is the same as 2-methylpropane.
Odour and Toxicity
Isopropanol, like other hazardous alcohols, is rapidly absorbed, with about 80% absorbed within 30 minutes of administration. Approximately 80% of the isopropanol ingested is metabolised by the liver via first-order kinetics and converted to acetone by the enzyme alcohol dehydrogenase. Isopropanol blood levels typically peak between 30 minutes and 3 hours after intake, with a half-life of 3 to 7 hours.
When isopropanol is co-ingested with ethanol, its half-life increases because ethanol has a stronger affinity for alcohol dehydrogenase than isopropanol, acetone, on the other hand, has a half-life of 22 hours and is mostly eliminated by the kidneys.
Isopropanol, often known as isopropyl alcohol, is a clear, colourless liquid with an odour similar to acetone. It is a commercially accessible substance mostly found in rubbing alcohol and hand sanitisers as a 70% solution.
Isopropanol, unlike other hazardous alcohols, seldom causes mortality and is linked with ketosis without acidosis. Isopropanol ingestions are routinely treated with supportive care, and ingestions are seldom fatal.
Synthesis of Iso Compounds
Chemical compounds are atoms from various elements held together by chemical bonds. Chemical synthesis generally entails breaking existing bonds and forming new ones.
In materials science, isoindoline has found widespread use. Isoindole-containing BODIPY dyes are extremely fluorescent compounds widely employed in various scientific applications. Most elements of the periodic table form coordination complexes with phthalocyanines, which are metal-containing cyclic tetramers of isoindole.
Important Questions
1. Why is isopropyl also known as sec-propyl, yet t-butyl is not known as neo-butyl?
At least five C atoms must be present when one C atom is connected with four C atoms. As a result, butyl cannot be neo. When a methyl group is added to the second position of isopropyl, it is transformed into t-butyl. Isopropyl alcohol is what this is.
2. Why is isopropyl also known as sec-propyl?
Since the functional group in isopropyl is linked to the second position, isopropyl is essentially 2-propyl. Butyl groups have four carbon atoms. T-butyl has four carbon atoms, one of which is bound to the other three.
Conclusion
2-methyl alkanes are usually prefixed with the word iso-, which stands for isomer. In other words, if a methyl group is found on the second carbon in a carbon chain, the prefix iso- might be used.
In organic chemistry, iso refers to an organic molecule that contains all carbon atoms except one in a continuous chain. This prefix is used to identify a chemical with a single branch in its carbon chain. In organic chemistry, the word Sec refers to the attachment of a secondary carbon.
FAQs on Iso Compounds: Structure, Properties and Uses
1. What is an iso compound in organic chemistry?
An iso compound is an organic molecule that features a methyl group attached to the second-to-last carbon atom of a continuous carbon chain. This structure creates a characteristic 'Y' shape or a single branch near the end of the main chain. For example, in isobutane, the main chain is three carbons long (propane), with a methyl group on the second carbon.
2. What is the general rule for using the 'iso' prefix in nomenclature?
The prefix 'iso' is used in the common naming system when all carbon atoms, except for one, form a continuous chain. This single branching methyl group must be located on the penultimate (second from the end) carbon atom of the longest chain. The name 'iso' is followed by the name of the alkane corresponding to the total number of carbon atoms in the molecule.
3. How do you identify the difference between iso-, sec-, and tert- prefixes?
These prefixes describe the branching at the point of attachment for an alkyl group or functional group:
- iso-: The group has a methyl branch on the second-to-last carbon of its longest chain. Example: Isopropyl group.
- sec-: (secondary) The functional group is attached to a secondary carbon atom (a carbon atom bonded to two other carbons). Example: sec-butyl alcohol.
- tert-: (tertiary) The functional group is attached to a tertiary carbon atom (a carbon atom bonded to three other carbons). Example: tert-butyl alcohol.
4. Can you provide some common examples of iso compounds?
Certainly. Some common examples of iso compounds include:
- Isobutane (IUPAC name: 2-methylpropane)
- Isopentane (IUPAC name: 2-methylbutane)
- Isohexane (IUPAC name: 2-methylpentane)
- Isopropyl alcohol (IUPAC name: propan-2-ol)
In each of these examples, there is a characteristic methyl group on the second carbon from the end of the parent chain.
5. What are some key properties and uses of common iso compounds?
Iso compounds have various important applications driven by their properties. For instance, isooctane is a crucial component in gasoline, where it serves as a standard for anti-knock properties. Isopropyl alcohol, or isopropanol, is widely used as a disinfectant and cleaning agent in rubbing alcohol and hand sanitizers. Isobutane is used as a refrigerant and a propellant in aerosol sprays, often as a replacement for ozone-depleting chlorofluorocarbons (CFCs).
6. Why is the 'iso' prefix typically used for compounds with at least four carbon atoms?
The 'iso' prefix requires a specific structure: a methyl group on the second-to-last carbon of a chain. The smallest molecule that can meet this condition is isobutane, which has a total of four carbon atoms. A molecule with three carbons, like propane, has no 'second-to-last' carbon for a methyl group to branch from without simply extending the chain. Therefore, the concept of an 'iso' isomer becomes meaningful only starting with butane (C₄H₁₀).
7. How do the physical properties, like boiling point, of an iso-alkane compare to its straight-chain isomer?
An iso-alkane generally has a lower boiling point than its corresponding straight-chain (n-alkane) isomer. This is because the branching in iso compounds makes the molecule more spherical and compact. This shape reduces the surface area available for intermolecular contact, leading to weaker van der Waals forces. Weaker forces require less energy to overcome, resulting in a lower boiling point. For example, n-butane boils at -0.5°C, while isobutane boils at -11.7°C.
8. Is the 'iso' prefix an official part of the IUPAC nomenclature system?
The 'iso' prefix is considered a common or trivial name and is not part of the systematic IUPAC nomenclature rules. However, due to widespread historical use, the IUPAC system has retained the use of 'iso' for some small, common alkanes like isobutane and isopentane as acceptable names. For more complex molecules, the systematic IUPAC method of identifying the parent chain and numbering substituents is always preferred for clarity.
9. Why is 2,2,4-trimethylpentane also called isooctane, when it does not fit the simple 'iso' structure?
The name 'isooctane' is a historical, common name that does not strictly follow the 'iso' structural rule. It refers to a specific, highly branched isomer of octane (C₈H₁₈) that is famously used as the 100-point standard for the octane rating of gasoline. The name likely arose from its synthesis process. While its official IUPAC name, 2,2,4-trimethylpentane, accurately describes its structure, the name 'isooctane' persists due to its significance in the petroleum industry.
10. What is the difference between an 'iso' compound in organic chemistry and an 'isostructural' compound in inorganic chemistry?
These terms describe two completely different concepts. An 'iso' compound in organic chemistry refers to a specific type of structural isomerism involving a branched carbon chain. In contrast, 'isostructural' is a term used in crystallography to describe two different chemical compounds that have the same crystal structure or arrangement of atoms in their solid state. For example, sodium nitrate (NaNO₃) and calcite (CaCO₃) are isostructural because their ions are arranged in the same way in their crystal lattices, despite different chemical compositions.
