Problem 28 - A Complete Resource Book in Chemistry for JEE Main

Question

The correct IUPAC name of \(\mathrm{AlCl}_{3}(\mathrm{EtOH})_{4}\) is (a) Aluminium (II) chloride-4-ethanol (b) Aluminium(III) chloride-4-ethanol (c) Aluminium(IV) chloride-4-hydroxy ethane (d) Aluminium chloride-4-ethanol

Step-by-Step Solution

Answer

(b) Aluminium(III) chloride-4-ethanol

Step 1: Determine Oxidation State of Aluminium

In the compound \( \text{AlCl}_3(\text{EtOH})_4 \), aluminium (\( \text{Al} \)) commonly exhibits an oxidation state of +3. This is because \( \text{AlCl}_3 \) is formed by the transfer of electrons between \( \text{Al}^{3+} \) and \( \text{Cl}^- \).

Step 2: Analyze the Ligands

The compound \( \text{AlCl}_3(\text{EtOH})_4 \) consists of \( \text{EtOH} \), which is ethanol. Ethanol is not involved in oxidation state changes, but acts as a ligand. Therefore, the correct naming involves counting these ligands.

Step 3: Construct the IUPAC Name

Based on the previous steps, the IUPAC name must include the oxidation state of aluminium and the number and type of ligands. Hence, the name should be 'Aluminium(III) chloride-4-ethanol', denoting the oxidation state +3 of aluminium and 4 ethanol ligands.

Step 4: Select the Correct Answer

Given the constructed IUPAC name, the answer that matches is (b) Aluminium(III) chloride-4-ethanol.

Key Concepts

Oxidation States

In chemistry, the oxidation state is a critical concept that helps us understand how atoms interact during chemical reactions. It indicates the degree of oxidation of an atom within a substance. The oxidation state is represented by an integer, which can be positive, negative, or zero. This number reflects the hypothetical charge an atom would have if all bonds were completely ionic.

In coordination compounds like \(\mathrm{AlCl}_{3}(\mathrm{EtOH})_{4}\), the oxidation state of aluminum (Al) is +3. This happens because aluminum loses three electrons, turning into \(\text{Al}^{3+}\), while each chlorine ion, \(\text{Cl}^-\), gains one electron. Understanding oxidation states is fundamental because it helps chemists predict the outcome of reactions.

To identify the oxidation state, follow these steps:

• Consider known oxidation states of common ions: \(\text{Cl}^-\) is -1, while \(\text{H}^+\) found in water and alcohols is usually +1.
• Assign the oxidation state to the central atom (like aluminum) based on its typical charge in compounds.
• Adjust numbers ensuring that the sum of oxidation states equals the compound's net charge.

Coordination Compounds

Coordination compounds consist of a central metal atom or ion bonded to surrounding molecules or ions, called ligands. These complexes are a key area in inorganic chemistry as they display unique properties and biological significance.

The central metal ion is often a transition metal, like iron, copper, or aluminum, as seen in \(\mathrm{AlCl}_3(\text{EtOH})_4\). These metals can form multiple bonds due to their d-orbitals. The central ion connects with ligands through coordinate-covalent bonds, creating a stable structure.

Here are some features of coordination compounds:

• Formation: Constructed by bonding ligands to a central metal ion.
• Examples: Vitamin B12 (cobalt center) and hemoglobin (iron center).
• Stability: Influenced by the metal ion's nature and the ligands' types.

Coordination compounds play roles in catalysis, material science, and medicine, highlighting their importance in different scientific fields.

Ligand Counting

Ligand counting is essential for understanding coordination compounds. It involves determining the number and types of ligands attached to the central metal atom. By knowing this, you can better understand the compound's geometry and reactivity.

In \(\mathrm{AlCl}_3(\text{EtOH})_4\), there are four ethanol (\(\text{EtOH}\)) ligands bonded to the aluminum ion. Despite being neutral species, these ligands occupy coordination sites around the metal, affecting the compound's properties and naming.

To effectively count ligands, follow this process:

• Identify all groups or molecules directly bonded to the central metal ion.
• Consider both charged and neutral species as potential ligands.
• Account for any multiple similar groups as individual ligands.

Understanding ligand counting provides clarity on a compound's structure, influencing factors like naming and predicted chemical behavior.

Inorganic Chemistry

Inorganic chemistry is a vast field of chemistry focused on inorganic compounds, which generally lack carbon-hydrogen bonds. This branch of chemistry covers a wide range of substances, including metals, minerals, salts, and coordination compounds.

In \(\mathrm{AlCl}_3(\text{EtOH})_4\), we see inorganic chemistry principles at work. Aluminum chloride forms a complex with ethanol ligands, showcasing the dynamic interactions between metals and simple molecules.

• Scope: Includes compounds in geological and biological systems.
• Applications: Ranges from catalysis to materials science and beyond.
• Diversity: Covers metals, nonmetals, acids, bases, and salts.

Inorganic chemistry paves the way for innovations in technology, pharmaceuticals, and environmental solutions, underlining its importance to our daily lives and scientific advancements.