Introduction
The molecular formula C11H15NO describes a class of organic compounds that contain eleven carbon atoms, fifteen hydrogen atoms, one nitrogen atom, and one oxygen atom. This stoichiometry is characteristic of amide-containing molecules in which a phenyl ring is connected to an alkyl chain that carries an amide functional group. The presence of the amide moiety (–C(=O)–NH–) confers notable hydrogen‑bonding capabilities, while the phenyl ring introduces aromatic stability. Because the formula allows for a variety of structural arrangements, numerous isomers exist, each with distinct physicochemical properties and potential applications.
Structural Features
Molecular Skeletons
Compounds with the formula C11H15NO commonly adopt one of the following skeletal frameworks:
- Linear aliphatic chains (C4–C5) attached to a phenyl ring through a nitrogen atom, forming N‑phenylalkyl amides.
- Branching at the carbon adjacent to the carbonyl, yielding N‑phenyl‑substituted acetamides with additional methyl groups.
- Conjugated systems where the carbonyl is part of an aromatic heterocycle (e.g., lactams) that retains the overall atomic counts.
- Ring‑based structures such as cycloalkyl amides fused to a phenyl group.
Each skeleton type influences electronic distribution, steric accessibility, and consequently, the compound’s reactivity and interaction with biological targets.
Conformational Considerations
Amide bonds exhibit partial double‑bond character, restricting rotation around the C–N axis. This rigidity leads to well‑defined cis/trans (E/Z) isomerism, especially in N‑phenyl derivatives where the phenyl ring can adopt planar or orthogonal orientations relative to the amide plane. The presence of alkyl substituents on the carbonyl carbon can further bias the conformational equilibrium by steric hindrance, affecting melting points and solubility.
Physical and Chemical Properties
Melting and Boiling Points
Melting points for representative isomers range from 45 °C to 120 °C, reflecting the balance between intermolecular hydrogen bonding and crystal packing efficiency. Boiling points are generally high (between 250 °C and 350 °C) due to the moderate molecular weight and strong intermolecular forces. Precise values depend on the exact substitution pattern; for instance, N‑phenylbutanamide has a melting point of 95 °C, whereas N‑phenyl‑2‑methylpropanamide melts at 70 °C.
Solubility
These amides are moderately soluble in polar protic solvents such as ethanol, methanol, and water (up to 10 mM at room temperature). Solubility decreases in nonpolar solvents like hexane. The phenyl ring contributes to lipophilicity, while the amide group enhances aqueous compatibility. Solvent effects are pronounced in chromatographic separations and crystallization procedures.
Spectroscopic Signatures
Infrared spectra exhibit a strong carbonyl absorption around 1650–1700 cm–1 and a characteristic N–H stretching band near 3300–3400 cm–1. NMR data typically reveal a singlet or multiplet for the amide proton (δ 7.8–8.4 ppm), aromatic protons in the δ 7.2–7.8 ppm region, and aliphatic signals between δ 0.9 and δ 2.8 ppm. Mass spectrometry provides a molecular ion peak at m/z = 181, confirming the formula C11H15NO.
Synthetic Approaches
Acylation of Anilines
The most straightforward route involves the reaction of an aniline derivative with a suitable acyl chloride or anhydride. For example, treating N‑phenylamine with 2‑bromobutanoyl chloride in the presence of a base yields N‑phenylbutanamide after work‑up. This method allows for the introduction of various alkyl groups on the acyl component, facilitating structural diversity.
Amide Formation via Carbodiimide Coupling
Carbodiimide reagents such as DCC (dicyclohexylcarbodiimide) or EDCI (1‑ethyl‑3‑(3‑dimethylaminopropyl)carbodiimide) mediate the coupling of carboxylic acids with amines under mild conditions. Reaction of 4‑phenylbutanoic acid with an appropriate amine in the presence of a coupling agent produces the desired amide while minimizing side reactions.
Reductive Amination of Carbonyl Compounds
Alkyl‑substituted phenyl aldehydes or ketones can be subjected to reductive amination with ammonia or primary amines, followed by oxidation to the amide. This two‑step sequence offers access to substituted amides that are otherwise difficult to prepare by direct acylation.
Ring‑Opening of Lactams
Certain cyclic amides (lactams) with the correct substitution pattern can be opened by nucleophilic attack, yielding open‑chain analogs while preserving the C11H15NO composition. For instance, a β‑lactam bearing a phenyl group can be converted to N‑phenylbutanamide via nucleophilic ring opening followed by protonation.
Applications
Pharmaceutical Intermediates
Amides bearing a phenyl ring are common motifs in drug design due to their ability to engage in π–π stacking and hydrogen bonding. Several analgesic and anti‑inflammatory agents incorporate the C11H15NO core as a scaffold. For example, derivatives of N‑phenylbutanamide are investigated for selective cyclooxygenase inhibition. Modifications at the N‑substituent and carbonyl position influence receptor affinity and metabolic stability.
Agricultural Chemicals
Certain amide‑containing compounds with this formula serve as intermediates in the synthesis of herbicides and fungicides. Their aromatic character allows for interaction with plant enzyme active sites, while the amide group enhances water solubility, facilitating formulation as aqueous sprays.
Material Science
Polymers incorporating C11H15NO units exhibit useful mechanical properties. For instance, polyamide chains with phenyl substituents display increased tensile strength and thermal resistance, making them suitable for high‑performance textiles and engineering plastics.
Analytical Standards
Because of their defined structure and stability, these amides are employed as internal standards in chromatographic and spectroscopic analyses. Their distinct UV absorption and mass spectral features enable accurate quantification of related compounds in complex matrices.
Safety and Environmental Considerations
Toxicological Profile
Compounds of this class generally exhibit low acute toxicity when handled under standard laboratory conditions. Oral LD50 values for representative isomers fall within the 2000–5000 mg kg–1 range in rodent models, indicating moderate toxicity. Skin and eye irritation are minimal, but prolonged exposure may cause mild dermatitis in susceptible individuals.
Environmental Impact
Amide functionalities are readily hydrolyzed by microbial enzymes in soil and water, leading to benign metabolites such as phenylamine and short‑chain carboxylic acids. Consequently, environmental persistence is low, though accumulation in aquatic systems can occur if concentrations exceed biodegradation capacities.
Regulatory Status
These molecules are not listed as regulated substances under major environmental or health protection frameworks. Nonetheless, local regulations may apply to specific derivatives that exhibit higher bioactivity or persistence. Good laboratory practice and proper waste disposal are recommended to mitigate any potential exposure risks.
Derivatives and Related Compounds
Variants of the C11H15NO scaffold include:
- N‑phenyl‑2‑methylpropanamide (C11H15NO) – a branched analogue with enhanced lipophilicity.
- 1‑Phenylpropane‑1‑amine carboxamide (C11H15NO) – incorporating a secondary amine moiety.
- 3‑Phenyl‑2‑butanone oxime O‑acetylhydroxylamine (C11H15NO) – a heteroatom‑modified derivative with distinct reactivity.
- Phenyl‑4‑methyloctanamide (C11H15NO) – a linear isomer featuring a methyl branch at the terminus.
These analogues demonstrate how minor structural alterations can lead to significant changes in biological activity, solubility, and metabolic pathways.
Analytical Techniques
Chromatography
High‑performance liquid chromatography (HPLC) using reverse‑phase columns separates C11H15NO isomers with a resolution that depends on the degree of branching. Gas chromatography (GC) is effective for volatile derivatives, such as the corresponding N‑methylated species, which have lower boiling points.
Spectroscopy
UV–Vis absorption peaks near 260 nm provide a quantitative handle for compounds bearing the phenyl ring. Raman spectroscopy can complement IR data, offering a stronger carbonyl band at 1675 cm–1 for certain isomers.
Mass Spectrometry
Electrospray ionization (ESI) and matrix‑assisted laser desorption/ionization (MALDI) yield clear molecular ion peaks at m/z = 181. Fragmentation patterns such as loss of H2O (–18 Da) or CH3OH (–32 Da) aid in confirming structural features.
Future Directions
Ongoing research explores the use of C11H15NO derivatives as ligands in organocatalysis, where the amide group can serve as a hydrogen‑bond donor in enantioselective transformations. Additionally, photophysical studies are investigating these compounds as potential photosensitizers for light‑driven chemical processes. Computational modeling continues to elucidate structure–activity relationships, guiding the synthesis of next‑generation analogues with improved efficacy.
Conclusion
Amide compounds with the empirical formula C11H15NO constitute a versatile class of molecules that bridge fundamental chemistry and applied sciences. Their predictable physicochemical behavior, accessible synthesis, and broad utility in pharmaceuticals, agriculture, and materials underscore their importance in contemporary research and development.
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