Related Experiment Video
Updated: Jun 12, 2025
11:45
Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles
Published on: August 22, 2018
8.4K
Effect of Solvent on the Optical Rotation of Azatryptophan Derivatives.
Mitalee Das1, Felix Kulandai1, Hemantha Kumar1
1Discovery Analytical Sciences, Biocon Bristol Myers Squibb Research & Development Center (BBRC), Bangalore, India.
Magnetic Resonance in Chemistry : MRC
|September 24, 2024
Summary
Chirally pure 7-azatryptophan derivatives exhibit solvent-dependent optical rotation. Hydrogen bonding between the derivatives and solvents influences the rotation
Area of Science:
- Organic Chemistry
- Stereochemistry
- Spectroscopy
Background:
- 7-azatryptophan is an analog of tryptophan, a crucial amino acid.
- Chiral molecules exist as non-superimposable mirror images (enantiomers).
- Optical rotation measures a chiral compound's interaction with plane-polarized light.
Purpose of the Study:
- To synthesize chirally pure 7-azatryptophan derivatives.
- To investigate the impact of solvent properties on optical rotation.
- To elucidate the role of hydrogen bonding in observed optical rotation changes.
Main Methods:
- Synthesis of protected 7-azatryptophan enantiomers.
- Measurement of optical rotation in various solvents.
- Characterization using proton nuclear magnetic resonance (1H NMR) spectroscopy.
Main Results:
- Synthesized enantiomers (R-3c, S-3c, R-3i, S-3i, R-3m, S-3m, R-3aa, S-3aa) displayed solvent-dependent optical rotation.
- Optical rotation values and signs varied with different solvents.
- Solvent electron-donating properties and donor numbers correlated with rotation changes.
- 1H NMR confirmed hydrogen bond formation between Fmoc NH and solvent donor groups.
Conclusions:
- Solvent interactions, particularly hydrogen bonding, significantly influence the optical rotation of 7-azatryptophan derivatives.
- The electron-donating capacity of solvents is a key factor in observed optical rotation variations.
- Intramolecular and intermolecular hydrogen bonds play a critical role in stereochemical behavior.
Related Concept Videos
02:24Properties of Enantiomers and Optical Activity
16.8K
It is essential to understand the difference between chiral and achiral interactions and the implications thereof in optical activity and their applications. Just as our feet, which are chiral, interact uniquely with chiral objects, such as a pair of shoes, but identically with achiral socks, enantiomers of a molecule exhibit different properties only when they interact with other chiral media. An example of a significant implication from this facet is the phenomenon known as optical activity,...
16.8K
02:12Solvating Effects
7.4K
An understanding of the solvating effect helps rationalize the relation between solvation and acidity of the compound. In addition, this also explains the relative stability of conjugate bases for compounds with different pKa values. This lesson details, in-depth, the principle of solvating effects. The strength of an acid and the stability of its corresponding conjugate base are determined using pKa values. This observed relationship is a consequence of solvation, which is the interaction...
7.4K
01:16Titration in Nonaqueous Solvents
765
Most acid-base titrations are performed in an aqueous medium. In aqueous titrations, water competes with weaker acids or bases for proton donation or acceptance, leading to ambiguous endpoints in the titration curve. Water also affects the partial ionization of weak acids or bases. For example, water accepts a proton from acetic acid to form hydronium and acetate ions. The hydronium ion formed is a stronger acid than acetic acid, and the acetate ion is a stronger base than water. As a result,...
765
01:17Chemical Shift: Internal References and Solvent Effects
620
In an NMR sample, precise measurement of the absolute absorption frequencies of nuclei is difficult. A standard internal reference compound is added, and the frequency difference between the reference signal and sample signals is measured.
The internal reference compound generally used in NMR spectroscopy is tetramethylsilane (TMS). TMS is preferred because it is chemically inert, soluble in NMR solvents, and easily removable. Also, the highly shielded methyl protons in TMS yield an intense...
The internal reference compound generally used in NMR spectroscopy is tetramethylsilane (TMS). TMS is preferred because it is chemically inert, soluble in NMR solvents, and easily removable. Also, the highly shielded methyl protons in TMS yield an intense...
620
01:15¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
1.1K
The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.
1.1K
02:19Physical Properties Affecting Solubility
22.5K
Solutions of Gases in Liquids
As for any solution, the solubility of a gas in a liquid is affected by the attractive intermolecular forces between solute and solvent species. Unlike solid and liquid solutes, however, there is no solute-solute intermolecular attraction to overcome when a gaseous solute dissolves in a liquid solvent since the atoms or molecules comprising a gas are far separated and experience negligible interactions. Consequently, solute-solvent interactions are the sole...
As for any solution, the solubility of a gas in a liquid is affected by the attractive intermolecular forces between solute and solvent species. Unlike solid and liquid solutes, however, there is no solute-solute intermolecular attraction to overcome when a gaseous solute dissolves in a liquid solvent since the atoms or molecules comprising a gas are far separated and experience negligible interactions. Consequently, solute-solvent interactions are the sole...
22.5K