Sample Solution

BCHET-147 Solved Assignment 2024 Sample Solution

bchet-147-solved-assignment-2024-ss-8e24e610-06c9-4b43-84f6-a5bf6ef5ab5c

PART A: ORGANOMETALLICS, BIOINORGANIC CHEMISTRY

1 Give the reactions where sodium nitroprusside is used for the qualitative analysis for the deterction of

S^{2 -}

and

S

in organic compounds.

Answer:

Sodium nitroprusside (Na₂[Fe(CN)₅NO]) is a reagent commonly used in qualitative analysis for the detection of sulfide ions (

S^{2 -}

) and elemental sulfur (

S

) in organic compounds. The reactions involved are:

Detection of Sulfide Ions ( $S^{2 -}$ ):

When sodium nitroprusside is added to a solution containing sulfide ions, a deep purple or violet coloration is produced due to the formation of a complex with the formula

[F e (C N)_{5} N O]^{2 -}

. The reaction can be represented as:

S^{2 -} + N a_{2} [F e (C N)_{5} N O] \to N a_{2} [F e (C N)_{5} N O S]

The purple color of the

[F e (C N)_{5} N O S]^{2 -}

complex is a characteristic test for the presence of sulfide ions in the sample.

Detection of Elemental Sulfur ( $S$ ):

For the detection of elemental sulfur in organic compounds, the sample is first treated with sodium or an alkali to convert the sulfur to sulfide ions:

S + 2 N a \to N a_{2} S

Then, sodium nitroprusside is added to the solution. If elemental sulfur was present in the original sample, the sulfide ions produced in the first step will react with sodium nitroprusside to give the same deep purple or violet coloration as mentioned above:

N a_{2} S + N a_{2} [F e (C N)_{5} N O] \to N a_{2} [F e (C N)_{5} N O S]

The appearance of the purple color indicates the presence of elemental sulfur in the organic compound.

In summary, sodium nitroprusside is a useful reagent for the qualitative analysis of sulfide ions and elemental sulfur in organic compounds, with the formation of a characteristic purple complex indicating the presence of these species.

2 Give the differences between organometallic compounds and organic compounds.

Answer:

Organometallic compounds and organic compounds are two distinct classes of compounds that differ in their composition, structure, and properties. Here are some key differences between them:

1. Composition:

Organometallic Compounds: These compounds contain at least one metal-carbon bond (M-C) where the metal is typically a transition metal, a lanthanide, or an actinide. The metal can be in a low oxidation state and can form complexes with organic ligands.
Organic Compounds: Organic compounds are primarily made of carbon and hydrogen atoms, and they may also contain other non-metal elements such as oxygen, nitrogen, sulfur, and halogens. There are no metal-carbon bonds in most organic compounds.

2. Bonding:

Organometallic Compounds: The metal-carbon bond in organometallic compounds can exhibit both ionic and covalent character, depending on the nature of the metal and the organic group. The bonding involves the interaction of the metal’s d orbitals with the carbon’s sp³, sp², or sp orbitals.
Organic Compounds: The bonding in organic compounds is predominantly covalent, involving the sharing of electrons between atoms. The carbon atoms typically form sp³, sp², or sp hybridized orbitals.

3. Reactivity:

Organometallic Compounds: Organometallic compounds are often highly reactive, especially towards air, moisture, and acids, due to the polar nature of the metal-carbon bond. They are commonly used as catalysts in various chemical reactions, such as cross-coupling reactions and olefin metathesis.
Organic Compounds: The reactivity of organic compounds varies widely depending on their functional groups and structure. They can undergo a range of reactions, including substitution, addition, elimination, and rearrangement reactions.

4. Applications:

Organometallic Compounds: These compounds are extensively used in catalysis, both in industrial processes and in laboratory synthesis. They are also employed in the development of new materials, as well as in organic light-emitting diodes (OLEDs) and other electronic applications.
Organic Compounds: Organic compounds have a wide range of applications in pharmaceuticals, plastics, fuels, dyes, agrochemicals, and many other industries.

5. Examples:

Organometallic Compounds: Ferrocene (Fe(C₅H₅)₂), Grignard reagents (RMgX, where R is an alkyl or aryl group and X is a halogen), and Wilkinson’s catalyst (RhCl(PPh₃)₃).
Organic Compounds: Methane (CH₄), benzene (C₆H₆), ethanol (C₂H₅OH), and acetic acid (CH₃COOH).

In summary, organometallic compounds are characterized by the presence of metal-carbon bonds and are often highly reactive, with significant applications in catalysis. In contrast, organic compounds are composed primarily of carbon and hydrogen, with a wide range of reactivities and applications across various industries.

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BCHET-147 Solved Assignment 2024