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Radical Substitution: Halogenation of Alkanes and Alkyl Substituents01:27

Radical Substitution: Halogenation of Alkanes and Alkyl Substituents

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In the initiation step of the reaction, the chlorine molecule undergoes homolytic cleavage in the presence of light or heat, forming two highly reactive chlorine radicals. Propagation occurs in two...
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Carboxylic acids react with diazomethane in an ether solvent via alkylation at the carboxylate oxygen atom to give methyl esters of the corresponding acid with excellent yields.
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Multiple Halogenation of Methyl Ketones: Haloform Reaction01:28

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A method involving the transformation of methyl ketones to carboxylic acids using excess base and halogen is called the haloform reaction. It begins with the deprotonation of α hydrogen to form an enolate ion which reacts with the electrophilic halogen to give an α-halo ketone. The step continues until all the α protons are substituted to form a trihalomethyl ketone. The resulting molecule is unstable, and in the presence of a hydroxide base, it readily undergoes nucleophilic...
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Mass Spectrometry: Alkyl Halide Fragmentation01:22

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Chlorine isotopes exist as 35Cl and 37Cl in a 3:1 ratio, while bromine isotopes exist as 79Br and 81Br in a 1:1 ratio. The mass spectrum of alkyl halides typically produces two distinct molecular ion peaks, the molecular ion peak, [M], and the molecular ion plus two, [M + 2] peak. The relative heights of these two peaks are proportional to the isotopic abundance ratios of the halide. For example, 2‐chloropropane and 1‐bromopropane display two peaks with relative peak heights in a 3:1 and...
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Inductive Effects on Chemical Shift: Overview01:27

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The protons in unsubstituted alkanes are strongly shielded with chemical shifts below 1.8 ppm. Methine, methylene, and methyl protons appear at approximately 1.7, 1.2 and 0.7 ppm, while the proton signal from methane appears at 0.23 ppm. An electronegative substituent, such as chlorine, withdraws the electron density from the protons, increasing their chemical shift. Progressive substitution of the hydrogens in methane by chlorine shifts the proton signals increasingly downfield, to 3.05 ppm in...
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Types of Toxins01:36

Types of Toxins

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Humans continually engage with an environment rich in potentially harmful chemicals. These are introduced to our bodies through inhalation, ingestion, or skin contact. These chemicals exist in various forms, such as air and environmental pollutants, agricultural chemicals, organic solvents, and heavy metals.
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Real-time Breath Analysis by Using Secondary Nanoelectrospray Ionization Coupled to High Resolution Mass Spectrometry
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Chloromethane emissions in human breath.

Frank Keppler1, Jan Fischer2, Tobias Sattler2

  • 1Institute of Earth Sciences, Heidelberg University, Im Neuenheimer Feld 234-236, 69120 Heidelberg, Germany; Heidelberg Center for the Environment (HCE), Heidelberg University, D-69120 Heidelberg, Germany.

The Science of the Total Environment
|July 4, 2017
PubMed
Summary

Humans exhale chloromethane (CH3Cl), a major atmospheric pollutant. This study detected CH3Cl in human breath, suggesting endogenous formation and potential implications for biochemistry and medical diagnostics.

Keywords:
Atmospheric global budgetBiochemical formationChlorinated organic compoundMethyl chlorideMethylation agent

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Area of Science:

  • Environmental Chemistry
  • Biochemistry
  • Human Physiology

Background:

  • Chloromethane (CH3Cl) is the most abundant atmospheric chlorinated organic compound.
  • CH3Cl contributes significantly to stratospheric ozone depletion.
  • Human emissions of CH3Cl have not been previously reported.

Purpose of the Study:

  • To investigate the endogenous formation and release of chloromethane in human breath.
  • To quantify CH3Cl concentrations in exhaled human breath.
  • To assess the potential contribution of human CH3Cl emissions to the global atmospheric source.

Main Methods:

  • Utilized a pre-concentration unit coupled with gas chromatography-mass spectrometry (GC-MS).
  • Measured CH3Cl concentrations in exhaled breath from 31 human subjects (ages 3-87).
  • Compared breath concentrations to ambient air levels.

Main Results:

  • All subjects exhaled CH3Cl at concentrations ranging from 2.5 to 33 parts per billion by volume.
  • Exhaled CH3Cl levels were significantly higher than inhaled air, by up to 60 times.
  • Estimated global human CH3Cl emissions at 0.66 Gg/yr, a minor contribution (<0.03%) to the total atmospheric source.

Conclusions:

  • Humans endogenously form and release chloromethane (CH3Cl).
  • The observed CH3Cl levels in breath warrant further investigation into its biochemical and medical significance.
  • CH3Cl's role as a potent methylating agent suggests potential as a diagnostic marker in medical research.