Jove
Visualize
Contact Us
JoVE
x logofacebook logolinkedin logoyoutube logo
ABOUT JoVE
OverviewLeadershipBlogJoVE Help Center
AUTHORS
Publishing ProcessEditorial BoardScope & PoliciesPeer ReviewFAQSubmit
LIBRARIANS
TestimonialsSubscriptionsAccessResourcesLibrary Advisory BoardFAQ
RESEARCH
JoVE JournalMethods CollectionsJoVE Encyclopedia of ExperimentsArchive
EDUCATION
JoVE CoreJoVE BusinessJoVE Science EducationJoVE Lab ManualFaculty Resource CenterFaculty Site
Terms & Conditions of Use
Privacy Policy
Policies

Related Concept Videos

¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR01:15

¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR

1.6K
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.
1.6K
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution00:52

¹H NMR of Conformationally Flexible Molecules: Temporal Resolution

1.2K
At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...
1.2K
¹H NMR: Complex Splitting01:13

¹H NMR: Complex Splitting

1.7K
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied...
1.7K
Factors Affecting Dissolution: Polymorphism, Amorphism and Pseudopolymorphism01:21

Factors Affecting Dissolution: Polymorphism, Amorphism and Pseudopolymorphism

619
Polymorphism refers to the existence of a drug substance in multiple crystalline forms, known as polymorphs. Recently, this term has been expanded to include solvates (forms containing a solvent), amorphous forms (non-crystalline forms), and desolvated solvates (forms from which the solvent has been removed).
Some polymorphic crystals possess lower aqueous solubility than their amorphous counterparts, leading to incomplete absorption. For instance, the oral suspension of Chloramphenicol, which...
619
¹H NMR: Interpreting Distorted and Overlapping Signals01:02

¹H NMR: Interpreting Distorted and Overlapping Signals

1.4K
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are...
1.4K

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by
Same author

Hydrogen Vacancy Induced Superconductivity Collapse in A15 Lanthanum Hydride.

Physical review letters·2026
Same author

Modulating Supramolecular Topology via Hydrogen Bonding in a Eumelanin Monomer.

Chemistry (Weinheim an der Bergstrasse, Germany)·2026
Same author

Erratum: "Developments and further applications of ephemeral data derived potentials" [J. Chem. Phys. 159, 144801 (2023)].

The Journal of chemical physics·2025
Same author

Author Correction: The first-principles phase diagram of monolayer nanoconfined water.

Nature·2025
Same author

Fast crystallographic texture mapping of atomically thin hBN films on Ni(111) using secondary electron contrast.

Nanoscale advances·2025
Same author

Prediction of novel gallium-sulfur compositions under pressure.

Physical chemistry chemical physics : PCCP·2025

Related Experiment Video

Updated: Dec 31, 2025

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
14:55

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy

Published on: September 17, 2017

15.9K

Identifying aspirin polymorphs from combined DFT-based crystal structure prediction and solid-state NMR.

Renny Mathew1, Karolina A Uchman1, Lydia Gkoura1

  • 1Division of Science, New York University Abu Dhabi, Abu Dhabi, UAE.

Magnetic Resonance in Chemistry : MRC
|January 5, 2020
PubMed
Summary

This study used computational modeling and solid-state NMR experiments to differentiate between aspirin polymorphs. The combined approach successfully identified form-I as the dominant crystal structure in the experimental sample.

Keywords:
1H NMRNMRNMR crystallographyab initio random structure searchingcrystal structure predictionorganic molecular crystalspharmaceuticalspolymorphismsmall molecules

More Related Videos

Construction and Systematical Symmetric Studies of a Series of Supramolecular Clusters with Binary or Ternary Ammonium Triphenylacetates
06:35

Construction and Systematical Symmetric Studies of a Series of Supramolecular Clusters with Binary or Ternary Ammonium Triphenylacetates

Published on: February 15, 2016

8.4K
Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR
14:44

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR

Published on: December 16, 2013

10.0K

Related Experiment Videos

Last Updated: Dec 31, 2025

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
14:55

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy

Published on: September 17, 2017

15.9K
Construction and Systematical Symmetric Studies of a Series of Supramolecular Clusters with Binary or Ternary Ammonium Triphenylacetates
06:35

Construction and Systematical Symmetric Studies of a Series of Supramolecular Clusters with Binary or Ternary Ammonium Triphenylacetates

Published on: February 15, 2016

8.4K
Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR
14:44

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR

Published on: December 16, 2013

10.0K

Area of Science:

  • Crystallography
  • Solid-state Chemistry
  • Pharmaceutical Science

Background:

  • Polymorphism in pharmaceutical drugs like aspirin can significantly impact their properties and efficacy.
  • Distinguishing between similar polymorphs requires advanced analytical techniques.
  • Accurate characterization of drug crystal forms is crucial for quality control and regulatory approval.

Purpose of the Study:

  • To develop and apply a combined computational and experimental method for distinguishing between aspirin polymorphs.
  • To accurately identify the specific crystalline form of aspirin present in an experimental sample.
  • To validate the effectiveness of ab initio random structure searching (AIRSS) and density functional theory (DFT) in polymorph identification.

Main Methods:

  • Utilized ab initio random structure searching (AIRSS) for predicting potential crystal structures of aspirin polymorphs.
  • Employed density functional theory (DFT) calculations to predict nuclear magnetic resonance (NMR) parameters for the predicted structures.
  • Conducted solid-state NMR experiments at natural abundance to obtain experimental NMR data for comparison.

Main Results:

  • AIRSS successfully predicted the crystal structures for both form-I and form-II of aspirin.
  • Calculated 1H chemical shifts from DFT were compared with experimental solid-state NMR data.
  • The root-mean-square deviation analysis of 1H chemical shifts allowed for the successful identification of form-I as the polymorph in the experimental sample.

Conclusions:

  • The integrated computational and experimental approach effectively distinguishes between closely related aspirin polymorphs.
  • DFT-calculated NMR parameters, validated by solid-state NMR experiments, are reliable for identifying crystalline forms.
  • This methodology provides a robust framework for polymorph characterization in pharmaceutical development.