Chinina - 10g

Quinine

Other Names: Quinine base, (R)-(6-Methoxyquinolin-4-yl)[(2S,4S,5R)-5-vinylquinuclidin-2-yl]methanol
Chemical Formula: C₂₀H₂₄N₂O₂
Molar Mass: 324.42 g/mol
CAS Number: 130-95-0
SMILES: COC1=CC2=C(C=CN=C2C=C1)[C@H](O)[C@@H]3C[C@H]4CCN3C[C@@H]4C=C
Appearance: White crystalline powder or colorless crystalline material
Odor: Odorless

Quinine is a naturally occurring quinoline alkaloid with a structurally complex, stereochemically defined molecular framework. Its structure contains a methoxy-substituted quinoline aromatic system connected through a secondary alcohol to a bicyclic quinuclidine moiety bearing a vinyl substituent. The molecule contains multiple stereogenic centers as well as two chemically distinct nitrogen atoms. These structural features give quinine characteristic basic, chiral, spectroscopic and photophysical properties. Quinine has played an important role in the development of alkaloid chemistry and remains extensively investigated in organic synthesis, asymmetric catalysis, analytical chemistry, fluorescence spectroscopy and molecular recognition.

Chemical and physical properties

Quinine in its free-base form is a crystalline organic solid with a molar mass of approximately 324.42 g/mol. The physical properties of quinine must be distinguished from those of its numerous salts, such as quinine hydrochloride and quinine sulfate, because salt formation substantially alters properties including solubility and thermal behavior.

Quinine is a basic compound containing a strongly basic tertiary quinuclidine nitrogen and a more weakly basic quinoline nitrogen. Protonation therefore depends on solution pH, and quinine can exist in neutral, mono-protonated and di-protonated forms. This acid-base behavior has a pronounced influence on its aqueous solubility, chromatographic retention and spectroscopic properties.

The free base has limited solubility in water but is considerably more soluble in many organic solvents. Conversion into protonated salts substantially increases its compatibility with aqueous media. The secondary alcohol, ether oxygen and nitrogen atoms provide sites for hydrogen bonding and other intermolecular interactions.

Quinine exhibits strong optical activity because of its multiple stereogenic centers. Its rigid chiral framework has consequently made quinine and structurally related Cinchona alkaloids important molecular platforms for investigations of stereochemistry, chiral recognition and asymmetric chemical transformations.

One of the most characteristic physicochemical properties of quinine is its fluorescence. In acidic aqueous media, protonated quinine exhibits intense blue fluorescence following ultraviolet excitation. Its fluorescence spectrum and quantum yield depend on factors including protonation state, solvent composition, temperature and concentration. Quinine sulfate solutions have consequently been extensively studied as fluorescence reference systems.

Applications

Quinine is widely used as a model fluorescent compound in photophysical and analytical research. Solutions of quinine salts in acidic media have historically served as fluorescence standards because their absorption and emission characteristics have been extensively characterized. Quinine-based systems are used in investigations of fluorescence quantum yields, quenching, excited-state processes and instrumental response.

In asymmetric organic synthesis, quinine and related Cinchona alkaloids are important chiral molecular scaffolds. Their combination of a rigid stereogenic framework, a basic tertiary amine, an aromatic quinoline system and a secondary alcohol enables interactions with substrates through ion pairing, hydrogen bonding and steric recognition.

Quinine derivatives are extensively investigated as organocatalysts and chiral auxiliaries. Chemical modification of the hydroxyl, quinoline and quinuclidine regions allows the steric and electronic properties of the molecular framework to be adjusted for different asymmetric transformations. Cinchona-derived catalysts have been investigated in enantioselective additions, substitutions, oxidations and phase-transfer reactions.

Quinine is also employed in analytical chemistry as a chiral selector or as a structural precursor to chiral stationary phases. Derivatives of quinine can discriminate between enantiomers through combinations of electrostatic interactions, hydrogen bonding, π interactions and steric complementarity. Such systems have been investigated in high-performance liquid chromatography and capillary electrophoresis.

In supramolecular chemistry, quinine serves as a useful model for studying molecular recognition involving protonated amines, aromatic heterocycles and hydrogen-bonding groups. Its well-defined stereochemistry enables detailed investigation of interactions between chiral molecules and their influence on complex formation.

Quinine additionally remains an important reference alkaloid in natural-product chemistry. Its structural complexity has stimulated extensive research into stereoselective synthesis, reaction mechanisms and total synthesis, contributing substantially to the development of modern synthetic organic chemistry.

Scientific references

Valeur, B.; Berberan-Santos, M. N. Molecular Fluorescence: Principles and Applications. Wiley-VCH, 2012. Scientific reference covering the photophysical behavior of quinine and its use in fluorescence measurements.

Melhuish, W. H. Quantum efficiencies of fluorescence of organic substances: effect of solvent and concentration of the fluorescent solute. Journal of Physical Chemistry, 1961, 65(2), 229–235. DOI: 10.1021/j100820a009.

Brouwer, A. M. Standards for photoluminescence quantum yield measurements in solution (IUPAC Technical Report). Pure and Applied Chemistry, 2011, 83(12), 2213–2228. DOI: 10.1351/PAC-REP-10-09-31.

Kacprzak, K.; Gawroński, J. Cinchona alkaloids and their derivatives: versatile catalysts and ligands in asymmetric synthesis. Synthesis, 2001, 961–998. DOI: 10.1055/s-2001-14566.

Song, C. E. Cinchona Alkaloids in Synthesis and Catalysis: Ligands, Immobilization and Organocatalysis. Wiley-VCH, 2009. Scientific reference covering the structure, stereochemistry and applications of quinine and related Cinchona alkaloids in asymmetric chemistry.

Safety
Signal Word: Warning

Hazard statement(s)
H302: Harmful if swallowed.
H317: May cause an allergic skin reaction.

Precautionary statement(s)
P261: Avoid breathing dust.
P264: Wash skin thoroughly after handling.
P272: Contaminated work clothing should not be allowed out of the workplace.
P280: Wear protective gloves.
P301 + P312: IF SWALLOWED: Call a POISON CENTER/doctor if you feel unwell.
P302 + P352: IF ON SKIN: Wash with plenty of water.

Supplemental Hazard Statements
Warning: Harmful if swallowed.
May cause an allergic skin reaction.
Avoid breathing dust.
Wash skin thoroughly after handling.
Contaminated work clothing should not be allowed out of the workplace.
Wear protective gloves.

First Aid Measures
General advice:
First aiders need to protect themselves. Show this material safety data sheet to the doctor in attendance.

If inhaled:
Move to fresh air. Call a physician if symptoms persist.

In case of skin contact:
Take off immediately all contaminated clothing. Rinse skin with water/shower. Consult a physician.

In case of eye contact:
After eye contact: rinse out with plenty of water. Remove contact lenses if present and continue rinsing.

If swallowed:
After swallowing: immediately make the victim drink water (two glasses at most). Consult a physician.

Handling and Storage
Storage Conditions: Store in a cool, dry, and well-ventilated area. Keep away from moisture and incompatible substances.
Handling Precautions: Avoid inhalation of dust. Use appropriate personal protective equipment such as gloves, eye protection, and respiratory protection when handling.