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 Experiment Videos

Eclipsed Isopropyl Conformations of Two Dimeric Hydrazines.

Stephen F. Nelsen1, Michael T. Ramm, J. J. Wolff

  • 1Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, Wisconsin 53706-1396.

The Journal of Organic Chemistry
|July 12, 1996
PubMed
Summary

The study reports X-ray structures of tetraazacyclotetradecane isomers, revealing eclipsed isopropyl conformations. Molecular calculations predict low energy for these conformations, but NMR shows a different stability in solution.

Related Concept Videos

You might also read

Related Articles

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

Sort by
Same author

Monoalkyldecaborane(14) Syntheses via Nucleophilic Alkylation and Hydroboration.

Inorganic chemistry·2001
Same author

Synthesis of New Stanna- and Germaundecaboranes.

Inorganic chemistry·2001
Same author

Synthesis, Characterization, and Solid-State Molecular Structures of Nitrosoarene Complexes of Osmium Porphyrins.

Inorganic chemistry·2001
Same author

Structure-Reactivity Studies in Copper(II)-Catalyzed Phosphodiester Hydrolysis.

Inorganic chemistry·2001
Same author

Structural Information from Hydrazine Radical Cation Optical Absorption Spectra.

The Journal of organic chemistry·2001

Area of Science:

  • Organic Chemistry
  • Crystallography
  • Computational Chemistry

Background:

  • Investigating the conformational preferences of tetraazacyclotetradecane derivatives.
  • Understanding the influence of alkyl substituents on molecular geometry.

Purpose of the Study:

  • To determine the X-ray crystal structures of two specific tetraazacyclotetradecane isomers: s4iPr and a4iPr.
  • To compare experimental conformational data with predictions from molecular mechanics (MM2) and semiempirical quantum mechanics (AM1) calculations.
  • To elucidate the factors governing the conformational asymmetry observed in the a4iPr isomer.

Main Methods:

  • X-ray crystallography to determine the solid-state structures of s4iPr and a4iPr.
  • Molecular mechanics (MM2) and semiempirical quantum mechanics (AM1) calculations to predict low-energy conformations.

Related Experiment Videos

  • (13)C-NMR spectroscopy to assess conformational stability in solution.

    • Main Results:

    • The crystal structures of s4iPr and a4iPr reveal anti conformations for the N-alkyl groups.
    • A key finding is the presence of an eclipsed conformation for one in-isopropyl group in both isomers.
    • MM2 and AM1 calculations predict low energy for these eclipsed conformations.
    • Solution NMR data indicate that the observed asymmetry in a4iPr (different isopropyl rotamers) is energetically favored, contradicting computational predictions.
    • The bicyclooctane derivative (3) is identified as an inadequate model for 4iPr conformations.

    Conclusions:

    • The study highlights discrepancies between calculated and experimentally observed conformational preferences in solution for tetraazacyclotetradecane derivatives.
    • Crystal packing forces do not explain the observed asymmetry in a4iPr; intrinsic molecular stability dictates the conformation in solution.
    • Further refinement of computational methods may be needed to accurately predict the conformational behavior of such complex organic molecules.