கொஞ்சம் கெமிஸ்ட்ரி ! - EP.011

 

Chemical Properties

• Formula: AgNO₂

• Molar Mass: 153.87 g/mol

• Appearance: Colorless to yellow crystals

• Odor: Odorless

• Density: 4.453 g/cm³ at 25°C

• Melting Point: 140°C (284°F)

• Solubility: Soluble in hot water, insoluble in ethanol

• Magnetic Susceptibility: -42.0·10⁻⁶ cm³/mol

Structure

Silver nitrite has a crystalline structure with silver ions (Ag⁺) and nitrite ions (NO₂⁻). The nitrite ion has a bent molecular geometry with an O-N-O bond angle of approximately 115°.

Preparation

Silver nitrite can be prepared through the reaction of silver nitrate (AgNO₃) with an alkali nitrite, such as sodium nitrite (NaNO₂). The reaction is as follows:

$${\text{<span style="font-family: Diphylleia;">AgNO</span>}}_{\mathrm{<span\; style="font-family:\; Diphylleia;">3</span>}}<span\; style="font-family:\; Diphylleia;">(</span>\mathrm{<span\; style="font-family:\; Diphylleia;">a</span>}\mathrm{<span\; style="font-family:\; Diphylleia;">q</span>}<span\; style="font-family:\; Diphylleia;">)</span><span\; style="font-family:\; Diphylleia;">+</span>{\text{<span style="font-family: Diphylleia;">NaNO</span>}}_{\mathrm{<span\; style="font-family:\; Diphylleia;">2</span>}}<span\; style="font-family:\; Diphylleia;">(</span>\mathrm{<span\; style="font-family:\; Diphylleia;">s</span>}<span\; style="font-family:\; Diphylleia;">)</span><span\; style="font-family:\; Diphylleia;">\to </span>{\text{<span style="font-family: Diphylleia;">NaNO</span>}}_{\mathrm{<span\; style="font-family:\; Diphylleia;">3</span>}}<span\; style="font-family:\; Diphylleia;">(</span>\mathrm{<span\; style="font-family:\; Diphylleia;">a</span>}\mathrm{<span\; style="font-family:\; Diphylleia;">q</span>}<span\; style="font-family:\; Diphylleia;">)</span><span\; style="font-family:\; Diphylleia;">+</span>{\text{<span style="font-family: Diphylleia;">AgNO</span>}}_{\mathrm{<span\; style="font-family:\; Diphylleia;">2</span>}}<span\; style="font-family:\; Diphylleia;">(</span>\mathrm{<span\; style="font-family:\; Diphylleia;">p</span>}\mathrm{<span\; style="font-family:\; Diphylleia;">r</span>}\mathrm{<span\; style="font-family:\; Diphylleia;">e</span>}\mathrm{<span\; style="font-family:\; Diphylleia;">c</span>}\mathrm{<span\; style="font-family:\; Diphylleia;">i</span>}\mathrm{<span\; style="font-family:\; Diphylleia;">p</span>}\mathrm{<span\; style="font-family:\; Diphylleia;">i</span>}\mathrm{<span\; style="font-family:\; Diphylleia;">t</span>}\mathrm{<span\; style="font-family:\; Diphylleia;">a</span>}\mathrm{<span\; style="font-family:\; Diphylleia;">t</span>}\mathrm{<span\; style="font-family:\; Diphylleia;">e</span>}<span\; style="font-family:\; Diphylleia;">)</span>\backslash text\{AgNO\}\_3\; (aq)\; +\; \backslash text\{NaNO\}\_2\; (s)\; \backslash rightarrow\; \backslash text\{NaNO\}\_3\; (aq)\; +\; \backslash text\{AgNO\}\_2\; (precipitate)$$

Alternatively, it can be produced by the reaction between silver sulfate (Ag₂SO₄) and barium nitrite (Ba(NO₂)₂).

Uses

• Oxidizing Agent: Silver nitrite is used as a general oxidizing agent in various chemical reactions.

• Production of Aniline Compounds: It is used in the synthesis of aniline compounds.

• Nucleophilic Substitution Reactions: Employed in Victor Meyer type nucleophilic substitution reactions with organobromides or organoiodides to form nitro compounds.

• Nitroalkene Synthesis: Used in the synthesis of nitroalkenes with nitryl iodide generated in-situ from silver nitrite and elemental iodine.

• Skeletal Editing: Involved in the synthesis of 1,2,3-benzothiadiazoles via skeletal editing (S,N-heteroarene ring transformation) of variously functionalized 2-halobenzothiazoles and benzothiazolinones.

Safety and Hazards

• Hazard Statements: H272 (May intensify fire; oxidizer), H302 (Harmful if swallowed), H315 (Causes skin irritation), H319 (Causes serious eye irritation), H400 (Very toxic to aquatic life)

• Precautionary Statements: P210 (Keep away from heat/sparks/open flames/hot surfaces. No smoking), P220 (Keep/Store away from clothing/combustible materials), P221 (Take any precaution to avoid mixing with combustibles), P264 (Wash hands thoroughly after handling), P270 (Do not eat, drink or smoke when using this product), P273 (Avoid release to the environment), P280 (Wear protective gloves/protective clothing/eye protection/face protection), P301+P312 (IF SWALLOWED: Call a POISON CENTER or doctor/physician if you feel unwell), P302+P352 (IF ON SKIN: Wash with plenty of soap and water), P305+P351+P338 (IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing), P321 (Specific treatment), P330 (Rinse mouth), P332+P313 (If skin irritation occurs: Get medical advice/attention), P337+P313 (If eye irritation persists: Get medical advice/attention), P362 (Take off contaminated clothing and wash before reuse), P370+P378 (In case of fire: Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide for extinction), P391 (Collect spillage), P501 (Dispose of contents/container in accordance with local/regional/national/international regulations)

• NFPA 704 (Fire Diamond): 2 (Health), 0 (Flammability), 2 (Reactivity)

• Lethal Dose (LD50): Not available

Environmental Impact

Silver nitrite is very toxic to aquatic life and should be handled with care to prevent environmental contamination. Proper disposal methods should be followed to minimize its impact on the environment.

Handling and Storage

• Handling: Use in well-ventilated areas; avoid inhalation and contact with skin and eyes; use appropriate personal protective equipment (PPE).

• Storage: Store in tightly sealed containers made of corrosion-resistant materials; keep away from incompatible substances such as bases and oxidizers.

Industrial Applications

• Silver Plating: Used in the silver plating process.

• Hair Dye: Employed in the formulation of hair dyes.

• Inks and Markers: Used in the production of inks and permanent marker pens.

• Water Analysis: Used for the preparation of standard sodium nitrite solutions for water analysis.

• Reagent: Used as a reagent for primary, secondary, and tertiary alcohols.

Chemical Reactions

• Reaction with Acids: Silver nitrite reacts with acids to form silver salts and nitrous acid (HNO₂).

• Reaction with Halides: Reacts with halides to form silver halides and nitrite ions.

Historical Background

Silver nitrite has been used in various chemical reactions and industrial applications for many years. Its unique properties as an oxidizing agent and its ability to participate in nucleophilic substitution reactions have made it a valuable compound in organic synthesis.

Molecular and Crystal Structure

The crystal structure of silver nitrite consists of silver ions (Ag⁺) and nitrite ions (NO₂⁻) arranged in a lattice. The nitrite ion has a bent molecular geometry with an O-N-O bond angle of approximately 115°.

Detection and Measurement

• Spectroscopy: Silver nitrite can be detected and measured using various spectroscopic techniques, including UV-Vis and IR spectroscopy.

• Titration: It can also be quantified using titration methods with appropriate indicators.

Purification

Silver nitrite can be purified by crystallization from hot conductivity water in the dark. It should be dried in the dark under vacuum to prevent decomposition.