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

1.2K
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.
1.2K
Mass Spectrometry: Long-Chain Alkane Fragmentation01:18

Mass Spectrometry: Long-Chain Alkane Fragmentation

1.8K
The molecular ions of linear alkanes prefer to fragment at the carbon-carbon bond away from the end of the chain since the cleavage of an inner bond creates a stable carbocation and a stable radical. Consequently, the mass signals of linear alkanes feature intense peaks in the middle of the mass-to-charge ratio plot with weaker peaks on either end. The fragmentation of each carbon-carbon bond with the release of a methyl group in each splitting leads to prominent peaks in the mass spectra...
1.8K
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution00:52

¹H NMR of Conformationally Flexible Molecules: Temporal Resolution

951
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...
951
Criteria for Aromaticity and the Hückel 4n + 2 Rule01:20

Criteria for Aromaticity and the Hückel 4n + 2 Rule

11.6K
Like benzene, cyclobutadiene and cyclooctatetraene are cyclic compounds with alternate single and double bonds. However, their chemical behavior differs from benzene, as they are unstable and not aromatic. So, what are the structural characteristics of unsaturated compounds categorized as aromatic?  
For the first time, Eric Hückel, a German chemical physicist, derived a set of structural features for a compound to be classified as aromatic. This is now known as...
11.6K
Degree of Unsaturation02:05

Degree of Unsaturation

8.9K
The degree of unsaturation (U), or index of hydrogen deficiency (IHD), is defined as the difference in the number of pairs of hydrogen atoms between the compound and the acyclic alkane with the same number of carbon atoms. Each double bond or ring costs two hydrogen atoms compared to a saturated analog and results in one degree of unsaturation.
The degree of unsaturation for hydrocarbons is U = (2C + 2 − H) / 2, where C is the number of carbon atoms and H is the number of hydrogen atoms.
8.9K
Reduction of Benzene to Cyclohexane: Catalytic Hydrogenation01:28

Reduction of Benzene to Cyclohexane: Catalytic Hydrogenation

5.1K
Unlike the easy catalytic hydrogenation of an alkene double bond, hydrogenation of a benzene double bond under similar reaction conditions does not take place easily. For example, in the reduction of stilbene, the benzene ring remains unaffected while the alkene bond gets reduced. Hydrogenation of an alkene double bond is exothermic and a favorable process. In contrast, to hydrogenate the first unsaturated bond of benzene, an energy input is needed; that is, the process is endothermic. This is...
5.1K

You might also read

Related Articles

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

Sort by
Same author

Establishment of exposure guidelines for lead in spacecraft drinking water.

Aviation, space, and environmental medicine·2014
Same author

Modeling of blood lead levels in astronauts exposed to lead from microgravity-accelerated bone loss.

Aviation, space, and environmental medicine·2014
Same author

Safe human exposure limits for airborne linear siloxanes during spaceflight.

Inhalation toxicology·2013
Same author

Ocular toxicity of authentic lunar dust.

BMC ophthalmology·2012

Related Experiment Video

Updated: Oct 7, 2025

On-line Analysis of Nitrogen Containing Compounds in Complex Hydrocarbon Matrixes
07:49

On-line Analysis of Nitrogen Containing Compounds in Complex Hydrocarbon Matrixes

Published on: August 5, 2016

10.8K

Acceptable Limits for n-Hexane in Spacecraft Atmospheres.

Hector D Garcia

    Aerospace Medicine and Human Performance
    |January 6, 2022
    PubMed
    Summary

    NASA

    Area of Science:

    • Aerospace Medicine
    • Toxicology
    • Environmental Health

    Background:

    • NASA's 2008 Spacecraft Maximum Allowable Concentrations (SMACs) for C2-C9 alkanes did not include n-hexane.
    • N-hexane poses a unique risk of polyneuropathy due to its metabolism, necessitating distinct safety limits.
    • Previous SMACs did not account for n-hexane's specific neurotoxic potential.

    Purpose of the Study:

    • To establish new, duration-specific Spacecraft Maximum Allowable Concentrations (SMACs) for n-hexane.
    • To address the neurotoxic risks associated with n-hexane exposure in spacecraft environments.
    • To provide updated exposure limits based on current toxicological data.

    Main Methods:

    • Comprehensive review of published toxicological studies on n-hexane.

    More Related Videos

    Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis
    14:11

    Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis

    Published on: March 29, 2016

    27.0K
    Preparation of a Corannulene-functionalized Hexahelicene by CopperI-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units
    09:35

    Preparation of a Corannulene-functionalized Hexahelicene by CopperI-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units

    Published on: September 18, 2016

    11.7K

    Related Experiment Videos

    Last Updated: Oct 7, 2025

    On-line Analysis of Nitrogen Containing Compounds in Complex Hydrocarbon Matrixes
    07:49

    On-line Analysis of Nitrogen Containing Compounds in Complex Hydrocarbon Matrixes

    Published on: August 5, 2016

    10.8K
    Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis
    14:11

    Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis

    Published on: March 29, 2016

    27.0K
    Preparation of a Corannulene-functionalized Hexahelicene by CopperI-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units
    09:35

    Preparation of a Corannulene-functionalized Hexahelicene by CopperI-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units

    Published on: September 18, 2016

    11.7K
  • Analysis of n-hexane's metabolic pathways and associated neurotoxicity in humans and rodents.
  • Development of exposure duration-specific concentration limits.

    • Main Results:

    • Recommended SMACs for n-hexane: 200 ppm (1 hour), 30 ppm (24 hours).
    • Recommended long-term SMACs for n-hexane: 2.4 ppm (7, 30, 180, and 1000 days).
    • These limits are more stringent than those for other C2-C9 alkanes.

    Conclusions:

    • The proposed SMACs for n-hexane mitigate risks of polyneuropathy from spacecraft exposure.
    • Updated exposure limits are crucial for astronaut health and safety.
    • This research provides critical data for NASA's environmental health standards.