Metandienone Wikipedia


3-Hydroxy-2-naphthoic acid (3‑Hydroxy‑2‑naphthoic acid)


IUPAC name: 3‑Hydroxy‑2‑naphthoic acid

Common name(s): Hydroxynaphthoic acid, 3‑HNA, 3‑Hydroxynaphthalene‑2‑acetic acid (when considered as a carboxylic acid derivative)




> Chemical formula: C₁₀H₈O₃

> Molecular weight: 180.15 g mol⁻¹

> Melting point: 145–147 °C (decomposition suspected)

> Appearance: White crystalline solid

> Solubility: Insoluble in water; soluble in ethanol, acetone, and dimethylformamide



---




1. Structural Overview



3‑Hydroxynaphthalene‑2‑acetic acid is a naphthyl‑substituted aromatic carboxylic acid with a hydroxyl group at the 3‑position of the naphthalene ring system.



IUPAC name:

3-hydroxy-2-naphthoic acid



Simplified structural formula:




O
||
HO—C6H4—C(=O)OH
(naphthyl)


The compound can be seen as a naphthalene ring bearing:




a carboxyl group at position 2,


an alcohol group at position 3.



Because of the conjugated aromatic system, this molecule is planar and highly delocalized. The resonance structures include charges localized on the oxygen atoms of the carboxyl group or the hydroxyl group, but the canonical form with the double bond between C=O remains dominant.

Key chemical features:




Feature Description


Aromaticity 6 π-electrons from the naphthalene core satisfy Huckel’s rule (4n+2).


Conjugation Carboxyl and hydroxyl groups extend the π-system.


Resonance Delocalization of electrons over the carbonyl group; possible charge separation on oxygens.


Acidity The hydroxyl proton is acidic due to resonance stabilization upon deprotonation, giving a conjugate base with extended delocalization.


---




2. Experimental Validation



2.1 Spectroscopic Confirmation of Resonance



Technique What it Probes Expected Observation Interpretation


IR spectroscopy (400–4000 cm⁻¹) C=O stretching A broadened, lower‑frequency (~1650 cm⁻¹) band indicates resonance with N lone pair. Shift to lower wavenumber reflects partial double‑bond character.


UV‑Vis absorption π→π transitions New absorption in visible region (if conjugated). Delocalization of electrons due to resonance.


NMR spectroscopy Chemical shift of H/N atoms Deshielded proton adjacent to C=O (~7–8 ppm) vs. typical amide ~6–7 ppm; ^15N shifts accordingly. Indicates electron withdrawal by C=O, enhanced by N lone pair donation.


These spectroscopic signatures confirm that the nitrogen’s lone pair participates in resonance with the carbonyl group.



---




4. Summary of Key Points



Aspect Observation


Electronic configuration \( \mathrmN\; (2p^3)\) and \( \mathrmC=O\; (2p^2)\).


Orbital interactions N’s sp²‑hybrid orbital overlaps with C=O π to give delocalized conjugated system.


Resonance effect Enhances stability of both nitrogen (partial double bond) and carbonyl (partial single bond).


Chemical consequence Lower reactivity toward nucleophiles/electrophiles; increased basicity/pKa; reduced electrophilicity of C=O.


---



This summarizes how the p‑orbitals of nitrogen and the carbonyl group interact to form a conjugated system.
We want to write an answer summarizing the interaction between p orbitals of N and the carbonyl group, forming a conjugated system.



We can include: description of the electronic structure, geometry, resonance structures, effect on reactivity (stabilization), etc. Provide bullet points or enumerated list.



Also mention typical examples: amides, imides, lactams, etc. Provide explanation about p orbitals aligning for conjugation, resulting in delocalization of electrons, leading to lower reactivity and increased stability. Also mention that the N's lone pair can be delocalized into the carbonyl pi orbital.



We need to produce a well-structured answer: maybe start with a brief introduction, then details: geometry, electronic structure, resonance forms, consequences on properties (stability, acidity of amide protons, etc.), typical examples. Use bullet points or numbers for clarity.



Let's write that.### Conjugation between an N‑bound lone pair and a carbonyl group





Feature Description


Geometry The C–O double bond is in the sp² plane. For conjugation, the nitrogen must also be coplanar with this plane (planarity ≈ 0° torsion). Most amides, imides and nitriles satisfy this because N‑C bonds are also sp².


Orbital overlap The nitrogen lone pair occupies an sp² orbital lying in the C–O plane. It can π‑overlap with the antibonding π\ orbital of the C=O (or C≡N) bond.

| Resulting delocalization | Resonance structures:

- For amides, N→C=O donation gives a partial double‑bond character to N–C and a negative charge on O.

- For imides (two carbonyls attached to the same nitrogen), the lone pair is shared between both C=O groups, enhancing resonance stabilization. |
| Effect on reactivity | The more delocalized the electron pair, the less basic it becomes; thus imide nitrogens are weaker bases than amide nitrogens, which in turn are weaker than simple amine nitrogens. This reduced basicity and increased resonance stabilization also make the carbonyl groups less electrophilic, altering their reactivity in nucleophilic addition or acylation reactions. |



---




Key Takeaways




Imide: nitrogen bonded to two carbonyl carbons (e.g., succinimide).


Amide: nitrogen bonded to one carbonyl carbon (e.g., acetamide).


The extra carbonyl in an imide increases resonance stabilization, leading to a less basic nitrogen and modified reactivity of the adjacent carbonyl groups compared with amides.



Feel free to ask for more details on specific reactions or examples!

Gender: Female

Social links