Methyl M-Nitrobenzoate: Properties, Uses & Guide

Methyl m-nitrobenzoate, a chemical compound integral to organic synthesis, exhibits distinct properties attributable to the nitro group’s influence on its benzene ring. The Sigma-Aldrich catalog lists methyl m-nitrobenzoate, specifying its purity and availability for laboratory use; thin-layer chromatography (TLC) serves as an analytical technique for assessing the purity of synthesized methyl m-nitrobenzoate. Dr. Carl Noller’s work in organic chemistry, particularly concerning the reactions and properties of aromatic compounds, provides a theoretical framework for understanding the reactivity of methyl m-nitrobenzoate. The substance’s role as an intermediate becomes significant in processes carried out within pharmaceutical research facilities and various industrial chemical reactions.

Unveiling Methyl m-Nitrobenzoate: A Cornerstone of Organic Synthesis

Methyl m-nitrobenzoate is an organic compound that holds a significant position in the realm of chemical synthesis and research. At its core, methyl m-nitrobenzoate is a derivative of benzoic acid, characterized by the presence of a nitro group (-NO₂) at the meta position relative to the ester functional group.

Its chemical formula, C₈H₇NO₄, succinctly captures its composition. This composition reveals key structural elements that dictate its reactivity and utility.

The Significance of a Synthetic Intermediate

In the intricate landscape of organic chemistry, certain compounds serve as pivotal synthetic intermediates. These compounds act as crucial building blocks in the creation of more complex molecules. Methyl m-nitrobenzoate unequivocally falls into this category.

Its unique structure makes it a versatile starting material for synthesizing a diverse range of compounds. These include pharmaceuticals, dyes, and other specialty chemicals. The presence of both the nitro and ester groups offers multiple avenues for chemical modification and functionalization.

Blog Post Objectives: A Comprehensive Exploration

This article embarks on a comprehensive exploration of methyl m-nitrobenzoate. Our journey will traverse several key aspects:

• Properties: We will dissect the compound’s physical and chemical characteristics, understanding how its structure dictates its behavior.

• Synthesis: We will delve into the synthetic routes employed to create methyl m-nitrobenzoate, highlighting the key reactions and considerations.

• Analytical Techniques: We will examine the analytical methods used to identify and characterize this compound, ensuring its purity and confirming its identity.

• Reactivity: We will investigate the types of chemical reactions that methyl m-nitrobenzoate undergoes. We will emphasize the influence of its functional groups.

• Safety: We will underscore the essential safety precautions necessary when handling this compound, prioritizing the well-being of researchers and the environment.

• Applications: Finally, we will illuminate the practical applications of methyl m-nitrobenzoate. We will focus on its role as a research chemical and its potential in various industrial sectors.

By addressing these critical facets, this article aims to provide a thorough understanding of methyl m-nitrobenzoate, solidifying its importance within the chemical sciences.

Decoding the Structure: Chemical and Physical Properties

Understanding the properties of methyl m-nitrobenzoate requires a careful examination of its molecular structure and the interplay of its constituent functional groups. The compound’s behavior is dictated by its status as a nitro compound, an ester, and a derivative of benzoic acid, each contributing unique characteristics to its overall chemical profile.

Significance of Functional Groups

Methyl m-nitrobenzoate’s chemical identity stems from the integration of three key functional components: the nitro group, the ester moiety, and its relationship to benzoic acid.

The Nitro Group’s Influence

The presence of the nitro group (-NO₂) is paramount. It exerts a powerful electron-withdrawing effect on the aromatic ring. This significantly impacts the reactivity of the molecule.

The electron-withdrawing nature deactivates the ring towards electrophilic aromatic substitution. It makes it less prone to reactions with electron-rich species.

The Ester Group’s Role

As an ester, methyl m-nitrobenzoate possesses a carbonyl group bonded to an alkoxy group. Esters are characterized by their susceptibility to hydrolysis and transesterification reactions.

Hydrolysis involves the cleavage of the ester bond by water, typically under acidic or basic conditions. Transesterification refers to the exchange of the alkoxy group with another alcohol. These reactions are crucial in various synthetic transformations.

Benzoic Acid Derivative

The core structure of methyl m-nitrobenzoate is derived from benzoic acid. This connection imparts inherent aromatic stability and reactivity patterns.

Modifications to the benzoic acid scaffold, such as the addition of the nitro group, alter the electronic properties. These alterations shift its chemical behavior.

Aromatic Nature

Methyl m-nitrobenzoate features an aromatic ring, which is the core of its structure. The benzene ring contributes to its stability and unique reactivity patterns.

The delocalized π-electron system within the ring provides enhanced stability. It renders the molecule resistant to addition reactions, favoring substitution reactions that maintain aromaticity.

Melting Point

The melting point of methyl m-nitrobenzoate is experimentally determined to be around 76-79 °C.

This value is indicative of the strength of the intermolecular forces holding the molecules together in the solid state.

The relatively moderate melting point suggests the presence of dipole-dipole interactions.

These dipole-dipole interactions arise from the polar nitro and ester groups, as well as weaker van der Waals forces.

Boiling Point

The boiling point of methyl m-nitrobenzoate is approximately 279 °C. The boiling point reflects the energy required to overcome the intermolecular forces in the liquid state.

The high boiling point (relative to its molecular weight) can be attributed to the same intermolecular forces influencing the melting point: dipole-dipole interactions and van der Waals forces.

Larger molecules with stronger intermolecular attractions typically exhibit higher boiling points.

Chemical Structure Diagram

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From Lab Bench to Vial: Synthesizing Methyl m-Nitrobenzoate

Crafting methyl m-nitrobenzoate in the laboratory is a meticulous process that showcases fundamental principles of organic synthesis. While several routes exist, the most common and efficient pathway involves the esterification of m-nitrobenzoic acid.

Let’s delve into the intricacies of this procedure, exploring the reagents, reaction mechanisms, and essential purification techniques.

Esterification of m-Nitrobenzoic Acid

The synthesis of methyl m-nitrobenzoate typically commences with m-nitrobenzoic acid as the starting material. This approach streamlines the process, bypassing the need for direct nitration of methyl benzoate which can lead to mixtures of isomers and reduce yields. The subsequent esterification reaction converts the carboxylic acid group of m-nitrobenzoic acid into the desired methyl ester.

The Role of Methanol and Acid Catalysts

The esterification process necessitates the use of methanol (CH₃OH) as both a reactant and a solvent, alongside an acid catalyst. Sulfuric acid (H₂SO₄) is commonly employed as the acid catalyst due to its effectiveness and availability. Other acids, such as hydrochloric acid (HCl) or p-toluenesulfonic acid (TsOH), can also be used but sulfuric acid remains a favorite for this transformation.

The acid catalyst plays a crucial role in activating the carbonyl group of the carboxylic acid, making it more susceptible to nucleophilic attack by methanol.

Esterification Reaction Mechanism Explained

The esterification reaction proceeds through a well-defined mechanism:

1. Protonation: The carbonyl oxygen of m-nitrobenzoic acid is protonated by the acid catalyst, increasing the electrophilicity of the carbonyl carbon.

2. Nucleophilic Attack: Methanol acts as a nucleophile, attacking the electrophilic carbonyl carbon. This forms a tetrahedral intermediate.

3. Proton Transfer: A proton transfer occurs within the tetrahedral intermediate, leading to the elimination of water.

4. Deprotonation: Deprotonation regenerates the acid catalyst and yields methyl m-nitrobenzoate.

Nitration of Benzene: An Alternative (and Less Favored) Route

While the esterification of m-nitrobenzoic acid is the preferred method, synthesizing methyl m-nitrobenzoate from benzene via nitration and subsequent reactions is possible but significantly more complex and less efficient.

Reagents for Nitration

The nitration of benzene requires a mixture of concentrated nitric acid (HNO₃) and concentrated sulfuric acid (H₂SO₄). This mixture generates the nitronium ion (NO₂⁺), the electrophile responsible for the substitution reaction.

Electrophilic Aromatic Substitution Mechanism

The nitration of benzene proceeds via electrophilic aromatic substitution (EAS).

1. Electrophile Formation: Sulfuric acid protonates nitric acid, leading to the formation of the nitronium ion.

2. Electrophilic Attack: The nitronium ion attacks the benzene ring, forming a sigma complex.

3. Deprotonation: A proton is removed from the sigma complex, restoring aromaticity and yielding nitrobenzene.

Directing Effects of Substituents

The m-nitro directing nature of the nitro group is important to consider if performing subsequent reactions. Already having a nitro group present would not allow for the reaction to occur at the meta position.

Purification by Recrystallization

After the esterification reaction is complete, the crude product typically contains impurities, such as unreacted m-nitrobenzoic acid, methanol, and the acid catalyst. Recrystallization is an essential technique to purify methyl m-nitrobenzoate.

Principles of Recrystallization

Recrystallization relies on the principle that a compound is more soluble in a hot solvent than in a cold solvent. By dissolving the crude product in a hot solvent and then slowly cooling the solution, the desired compound will crystallize out, leaving impurities dissolved in the solvent.

Choosing the Right Solvent

Selecting an appropriate solvent is crucial for successful recrystallization. The ideal solvent should dissolve the compound at high temperatures and sparingly at low temperatures. Common solvents include ethanol, methanol, and ethyl acetate. The choice of solvent depends on the solubility characteristics of methyl m-nitrobenzoate and the nature of the impurities.

Reaction Schemes

The following reaction schemes illustrate the synthesis of methyl m-nitrobenzoate.

Esterification:

[Insert Chemical Reaction Scheme Here: m-Nitrobenzoic acid + Methanol (H₂SO₄ catalyst) -> Methyl m-Nitrobenzoate + Water]

Nitration (Alternative Route):

[Insert Chemical Reaction Scheme Here: Benzene + HNO₃/H₂SO₄ -> Nitrobenzene]

Identifying the Compound: Analytical Techniques

Following the synthesis of methyl m-nitrobenzoate, rigorous analytical techniques are employed to confirm its identity and assess its purity. These methods, primarily spectroscopic and chromatographic, provide essential data for characterizing the compound. Accurate interpretation of this data is crucial for validating the success of the synthesis and ensuring the quality of the final product.

Nuclear Magnetic Resonance (NMR) Spectroscopy

NMR spectroscopy is a powerful tool for elucidating the structure of organic molecules. It relies on the interaction of atomic nuclei with a strong magnetic field, providing detailed information about the connectivity and environment of atoms within the molecule.

Interpreting the ¹H NMR Spectrum of Methyl m-Nitrobenzoate

The ¹H NMR spectrum of methyl m-nitrobenzoate exhibits distinct signals corresponding to the aromatic protons and the methyl group. The aromatic protons, due to the electron-withdrawing nature of the nitro and ester groups, are deshielded and appear downfield in the spectrum. Expect to see four distinct signals corresponding to the four aromatic protons.

The methyl protons of the ester group are typically observed as a singlet at around δ 3.9 ppm. This signal is due to the chemical environment of the methyl protons, which are adjacent to the electron-withdrawing oxygen atom of the ester group.

Interpreting the ¹³C NMR Spectrum of Methyl m-Nitrobenzoate

The ¹³C NMR spectrum provides information about the carbon atoms in the molecule. In methyl m-nitrobenzoate, the spectrum reveals distinct signals for the carbonyl carbon of the ester group (typically around δ 165 ppm), the aromatic carbons, and the methyl carbon (around δ 52 ppm). The chemical shifts of the aromatic carbons are influenced by the electron-withdrawing effects of the nitro and ester substituents.

Infrared (IR) Spectroscopy

IR spectroscopy is another valuable technique for identifying functional groups within a molecule. It measures the absorption of infrared radiation by the molecule, which causes vibrations of chemical bonds. The frequencies at which these vibrations occur are characteristic of specific functional groups.

Key Peaks in the IR Spectrum of Methyl m-Nitrobenzoate

The IR spectrum of methyl m-nitrobenzoate exhibits strong absorptions corresponding to the ester carbonyl group (C=O) and the nitro group (NO₂). The carbonyl absorption typically appears around 1720-1740 cm⁻¹, while the nitro group shows characteristic absorptions at approximately 1530 cm⁻¹ and 1350 cm⁻¹.

Mass Spectrometry (MS)

Mass spectrometry is a technique used to determine the molecular weight and fragmentation pattern of a compound. The molecule is ionized, and the resulting ions are separated according to their mass-to-charge ratio (m/z). The molecular ion peak, corresponding to the intact molecule, provides the molecular weight.

The fragmentation pattern can provide valuable information about the structure of the molecule, as specific bonds tend to break preferentially, giving rise to characteristic fragment ions. For methyl m-nitrobenzoate, expected fragments might include loss of the methyl group (CH₃) or the nitro group (NO₂).

Thin Layer Chromatography (TLC)

TLC is a simple and versatile chromatographic technique used for reaction monitoring and purity assessment. A small amount of the sample is spotted onto a TLC plate, which is then placed in a developing chamber containing a solvent. The solvent travels up the plate, separating the components of the sample based on their polarity.

Determining the Rf Value

The retention factor (Rf) is a measure of how far a compound travels on a TLC plate relative to the solvent front. It is calculated as the distance traveled by the compound divided by the distance traveled by the solvent front.

Solvent Systems for TLC

The choice of solvent system is crucial for achieving good separation on TLC. For methyl m-nitrobenzoate, a mixture of ethyl acetate and hexanes is commonly used. The ratio of these solvents can be adjusted to optimize the separation based on the compound’s polarity. More polar solvents will cause the compound to travel further up the plate, resulting in a higher Rf value.

TLC for Purity Assessment

TLC can be used to assess the purity of methyl m-nitrobenzoate by looking for the presence of additional spots on the plate. A pure sample should exhibit only one spot, corresponding to the desired compound. The presence of multiple spots indicates the presence of impurities.

Representative Spectra and Chromatograms

(Note: In a real blog post, this section would include actual NMR, IR, and MS spectra, as well as representative TLC plates, to illustrate the points made in the text. These visuals are essential for readers to understand the analytical data.)

Reactivity and Transformations: Chemical Properties in Action

Following the identification and characterization of methyl m-nitrobenzoate, understanding its chemical reactivity is paramount. This section delves into the transformations this compound undergoes, influenced by its unique structural features, and outlines its behavior under various reaction conditions.

Hydrolysis Reactions

The ester functionality of methyl m-nitrobenzoate makes it susceptible to hydrolysis, a reaction where the ester bond is cleaved by water. This process can occur under both acidic and basic conditions.

Acid-catalyzed hydrolysis involves the protonation of the carbonyl oxygen, followed by nucleophilic attack by water. This leads to the formation of m-nitrobenzoic acid and methanol.

Base-catalyzed hydrolysis, or saponification, proceeds through nucleophilic attack by hydroxide ion on the carbonyl carbon. This yields the m-nitrobenzoate salt and methanol. The salt can then be protonated with a strong acid to regenerate the m-nitrobenzoic acid.

Reduction Reactions

The nitro group on methyl m-nitrobenzoate is highly susceptible to reduction. A variety of reducing agents can be employed to transform the nitro group into other functional groups.

Catalytic hydrogenation, using a metal catalyst such as palladium on carbon (Pd/C), can reduce the nitro group to an amine (m-aminobenzoate). This reaction is highly valuable as it introduces a versatile functional group for further derivatization.

Selective reduction can be achieved using milder reducing agents, such as tin(II) chloride (SnCl2), to yield the corresponding hydroxylamine or nitroso compound, depending on the reaction conditions. Careful control of the reaction conditions is crucial to prevent over-reduction.

Impact of the Nitro Group

The nitro group (m-nitrobenzoate) significantly impacts the reactivity of the aromatic ring through its strong electron-withdrawing inductive (-I) and mesomeric (-M) effects.

The meta-directing effect of the nitro group deactivates the ortho and para positions of the ring, making them less prone to electrophilic attack. This directing effect is critical in controlling the regioselectivity of further substitutions on the aromatic ring.

The electron-withdrawing nature of the nitro group also increases the acidity of protons on adjacent carbon atoms, influencing the compound’s behavior in reactions involving deprotonation.

Transformations Involving the Ester Group

Beyond hydrolysis, the ester group in methyl m-nitrobenzoate can undergo various transformations.

Transesterification reactions allow for the exchange of the methyl group with other alcohols, leading to the formation of different ester derivatives. This is typically catalyzed by acids or bases.

The ester can also undergo reduction to form an alcohol. For example, using a strong reducing agent like lithium aluminum hydride (LiAlH4), both the ester and nitro groups will be reduced. Selective reduction can be achieved with milder reducing agents.

Reaction Schemes

Illustrative reaction schemes outlining these transformations are essential for a complete understanding of the chemical behavior of methyl m-nitrobenzoate. These schemes visually represent the flow of electrons and the changes in bonding during each reaction, providing a valuable tool for chemists and students alike.

Safe Handling Practices: Protecting Yourself and the Environment

Following the exploration of methyl m-nitrobenzoate’s reactivity, a critical consideration is the implementation of stringent safety protocols for its handling. The safe manipulation of any chemical compound requires a comprehensive understanding of its potential hazards and the appropriate measures to mitigate risks to personnel and the environment. This section details the necessary precautions for handling methyl m-nitrobenzoate, emphasizing the importance of personal protective equipment (PPE), proper ventilation, and responsible disposal methods.

The Safety Data Sheet: Your Primary Resource

Before commencing any work with methyl m-nitrobenzoate, or any chemical for that matter, consulting the Safety Data Sheet (SDS) is paramount. The SDS serves as a comprehensive repository of critical safety information, providing detailed guidance on a substance’s hazards, safe handling practices, and emergency procedures.

Key Information within the SDS

The SDS contains a wealth of information vital for safe handling, including:

• Hazard Identification: This section outlines the potential hazards associated with the compound, such as flammability, toxicity, and environmental risks.

• First Aid Measures: In the event of accidental exposure, the SDS provides detailed instructions on appropriate first aid procedures.

• Handling and Storage: This section specifies the recommended handling and storage conditions to minimize the risk of accidents or degradation of the compound.

• Exposure Controls/Personal Protection: This crucial section details the necessary PPE and engineering controls to protect personnel from exposure.

• Spill Cleanup Measures: The SDS outlines the proper procedures for containing and cleaning up spills, minimizing environmental impact.

Personal Protective Equipment: Your First Line of Defense

The use of appropriate Personal Protective Equipment (PPE) is essential for minimizing exposure to methyl m-nitrobenzoate. The minimum recommended PPE includes:

• Gloves: Impervious gloves, such as nitrile or neoprene, should be worn at all times to prevent skin contact. The specific glove material should be selected based on its resistance to the chemical.

• Safety Glasses: Chemical splash goggles or safety glasses with side shields are crucial for protecting the eyes from splashes or vapor exposure.

• Lab Coat: A laboratory coat provides a protective barrier for clothing and skin, preventing contamination from spills or splashes.

It is imperative to ensure that all PPE is in good condition and properly fitted before handling methyl m-nitrobenzoate.

Engineering Controls: Ventilation is Key

The implementation of engineering controls, particularly the use of a fume hood, is critical for minimizing exposure to airborne vapors of methyl m-nitrobenzoate.

The fume hood provides a ventilated workspace that effectively removes hazardous vapors, preventing inhalation and reducing the risk of systemic exposure.

All procedures involving methyl m-nitrobenzoate should be conducted within a properly functioning fume hood.

Understanding Toxicity and Potential Health Hazards

Methyl m-nitrobenzoate, like many organic compounds, presents potential health hazards upon exposure. While the specific toxicity profile may vary, potential health risks can include:

• Skin and Eye Irritation: Direct contact can cause irritation and inflammation.

• Respiratory Irritation: Inhalation of vapors may lead to respiratory irritation and discomfort.

• Systemic Effects: Depending on the route and duration of exposure, systemic effects may occur.

It is crucial to be aware of these potential hazards and to take appropriate precautions to minimize exposure.

Responsible Disposal Methods: Protecting the Environment

The proper disposal of methyl m-nitrobenzoate and contaminated materials is essential for protecting the environment. Under no circumstances should the compound be poured down the drain.

Waste disposal should be conducted in accordance with all applicable local, state, and federal regulations. Typically, waste methyl m-nitrobenzoate should be collected in a designated hazardous waste container and disposed of through a licensed hazardous waste disposal service. Consult your institution’s environmental health and safety department for specific disposal guidelines.

Real-World Applications: Where Methyl m-Nitrobenzoate Shines

Following the discussion of safety protocols, it is essential to consider the tangible applications of methyl m-nitrobenzoate, moving beyond theoretical considerations to examine its utility in practical contexts. While not a widely consumed bulk chemical, its specific properties render it valuable in specialized areas of research and development.

A Key Reagent in Organic Synthesis

Methyl m-nitrobenzoate primarily serves as a crucial intermediate in organic synthesis. Its unique structure, possessing both an ester and a nitro group positioned meta to each other on a benzene ring, allows for a variety of chemical manipulations.

This compound acts as a versatile building block, enabling chemists to construct more complex molecules with tailored functionalities. The nitro group, for instance, can be selectively reduced to an amine, opening pathways to a diverse range of aromatic compounds.

The ester moiety can be hydrolyzed to the corresponding carboxylic acid or transesterified to other esters, providing further avenues for structural modification.

Potential Applications in Pharmaceuticals and Agrochemicals

While direct applications of methyl m-nitrobenzoate in pharmaceuticals and agrochemicals are not extensively documented, its role as a synthetic precursor is significant.

Many complex pharmaceutical molecules contain aromatic rings with various substituents. Methyl m-nitrobenzoate can serve as a starting material for introducing specific patterns of substitution on such rings.

For example, it can be used in the synthesis of building blocks for pharmaceuticals that target specific biological pathways. In agrochemistry, similar logic applies. It can contribute to the synthesis of new pesticides or herbicides with enhanced selectivity and efficacy.

Precursor to Other Compounds

Methyl m-nitrobenzoate plays a pivotal role in the synthesis of various other compounds, often serving as an intermediate in multi-step synthetic routes.

It finds usage in the creation of dyes, pigments, and specialty chemicals. Its meta-substituted nitrobenzoate structure is often exploited to create molecules with specific electronic or steric properties.

The carefully controlled modification of the nitro and ester groups allows for targeted synthesis of molecules with a range of applications. The strategic placement of the nitro group influences the reactivity and regioselectivity of subsequent reactions, making it a valuable synthon in the hands of skilled chemists.

In essence, methyl m-nitrobenzoate’s contribution lies not in its direct application, but in its ability to serve as a stepping stone towards more complex and functional molecules. Its unique structure offers a strategic advantage in achieving specific synthetic goals.

So, there you have it! A quick look into the fascinating world of methyl m-nitrobenzoate. Hopefully, this guide has shed some light on its properties, uses, and maybe even sparked a little curiosity about this interesting chemical compound. Whether you’re a seasoned chemist or just starting out, we hope you found this helpful!