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Related Concept Videos

NMR and Mass Spectroscopy of Carboxylic Acids01:30

NMR and Mass Spectroscopy of Carboxylic Acids

4.0K
In ¹H NMR spectroscopy, acidic protons (–COOH) of carboxylic acids are highly deshielded and absorb far downfield, at around 9–12 ppm. The chemical shift value depends on the concentration and solvent used.
While α protons of carboxylic acids absorb at 2–2.5 ppm, β protons absorb further upfield.
Carboxylic acids are easily identified by dissolving them in deuterium oxide, which results in a rapid exchange of the acidic protons with deuterium. This leads to the...
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Masking and Demasking Agents01:19

Masking and Demasking Agents

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EDTA titrations may necessitate masking and demasking agents to temporarily protect a particular metal ion in a mixture from the EDTA reaction. These agents facilitate the sequential analysis of the metal ions by forming stable complexes with some—but not all—metal ions during certain steps.
There are many masking agents, such as cyanide, fluoride, triethanolamine, thiourea, and 2,3-bis(sulfanyl)propan-1-ol (formerly 2,3-dimercapto-1-propanol), with the masking agent chosen based on...
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IR and UV–Vis Spectroscopy of Carboxylic Acids01:28

IR and UV–Vis Spectroscopy of Carboxylic Acids

4.2K
In IR spectroscopy of carboxylic acids, the C=O bond shows a characteristic band between 1710 and 1760 cm⁻¹, and the O–H bond exhibits a broad band between 2500 and 3300 cm⁻¹.
However, the stretching absorptions for the C=O bond vary depending on the structure of carboxylic acids. The C=O bond of the free carboxylic acids shows a higher stretching frequency, 1760 cm−1, while H-bonded carboxylic acids (dimers) exhibit stretching absorptions at a lower frequency,...
4.2K
¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)01:20

¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)

1.1K
When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...
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Spectroscopy of Carboxylic Acid Derivatives01:26

Spectroscopy of Carboxylic Acid Derivatives

2.4K
Infrared spectroscopy is primarily used to determine the types of bonds and functional groups. In carboxylic acid derivatives, a typical carbonyl bond absorption is observed around 1650–1850 cm−1. For esters, the absorption is recorded at around 1740 cm−1, while acid halides show the absorption at about 1800 cm−1. Another acid derivative, the acid anhydrides, exhibit two carbonyl absorption around 1760 cm−1 and 1820 cm−1, arising from the symmetrical and...
2.4K
Stereochemical Effects of Enolization01:12

Stereochemical Effects of Enolization

2.0K
The chiral α-carbon of the carbonyl compound is the stereocenter of the molecule. As shown in the figure below, when such a carbonyl compound undergoes racemization under an acidic or basic condition, an achiral enol is formed.
2.0K

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Related Experiment Video

Updated: Jul 11, 2025

Real-time In Vitro Monitoring of Odorant Receptor Activation by an Odorant in the Vapor Phase
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Masking effects on iso-valeric acid recognition by sub-threshold odor mixture.

Jianbo Huang1, Jiehua Lin1, Rachel Yueng1

  • 1Department of Food Science, Cornell University, Ithaca, NY 14850, United States.

Chemical Senses
|November 13, 2023
PubMed
Summary

Masking unpleasant body odor, like that from iso-valeric acid (IVA), can be improved with specific masking agents. A mixture of six agents significantly reduced IVA recognition by 96%.

Keywords:
isovaleric acidodor coveringodor interactionodor suppressionolfactory codingolfactory receptors

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Area of Science:

  • Olfactory science
  • Psychophysics
  • Sensory perception

Background:

  • Odor masking is a common strategy in consumer products but its effectiveness is variable.
  • Iso-valeric acid (IVA), found in sweat, is a mal-odorant often requiring mitigation.
  • Traditional methods use high concentrations of masking agents, which may not be ideal.

Purpose of the Study:

  • To investigate the psychophysics of odor masking using Sniff olfactometry (SO).
  • To evaluate the effectiveness of sub-threshold concentrations of various masking agents on iso-valeric acid (IVA) recognition.
  • To determine the impact of odor mixtures on masking efficacy.

Main Methods:

  • Utilized Sniff olfactometry (SO) for precise odor delivery and perception measurement.
  • Administered brief (70 ms) stimulations with mixtures of IVA and masking agents.
  • Measured the probability of recognizing IVA under different masking conditions with nine subjects.

Main Results:

  • Individual masking agents decreased IVA recognition probability by an average of 14-72%.
  • A mixture of six sub-threshold masking agents significantly reduced IVA recognition.
  • The odor mixture demonstrated a substantial 96% decrease in IVA recognition probability.

Conclusions:

  • Sub-threshold masking agents can effectively reduce the perception of unpleasant odors like IVA.
  • Odor mixtures composed of multiple masking agents show enhanced efficacy compared to single agents.
  • This research provides insights into optimizing odor masking strategies for consumer applications.