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Preparation and Reactions of Sulfides

Preparation and Reactions of Sulfides

Sulfides are the sulfur analog of ethers, just as thiols are the sulfur analog of alcohol. Like ethers, sulfides also consist of two hydrocarbon groups bonded to the central sulfur atom. Depending upon the type of groups present, sulfides can be symmetrical or asymmetrical. Symmetrical sulfides can be prepared via an SN2 reaction between 2 equivalents of an alkyl halide and one equivalent of sodium sulfide.

Ladder Diagrams: Acid–Base Equilibria

Ladder Diagrams: Acid–Base Equilibria

Understanding the chemistry between the reagents is necessary for performing any experiment. To this end, scientists have designed a tool called a ladder diagram, which is a graphical representation that helps illustrate the chemistry of a system.
A ladder diagram for acid-base equilibria consists of a vertical axis that represents pH and horizontal bars (steps on the ladder) that help position all the pKa values in the system. At equilibrium, the pH value of the system corresponds to one of...

Precipitation and Co-precipitation

Precipitation and Co-precipitation

Precipitation and coprecipitation methods can be used to separate a mixture of ions in a solution. In qualitative inorganic analysis, ions that form sparingly soluble precipitates with the same reagent are separated based on the differences in solubility products. For example, consider the separation of Cu(II) and Fe(II) ions by precipitation as insoluble sulfides. First, copper(II) sulfide is precipitated by the addition of acidic H2S, where the dissociation of H2S is suppressed. Adding H2S...

Degree of Unsaturation

Degree of Unsaturation

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.
For...

Composition of Polyprotic Acid Solutions as a Function of pH

Composition of Polyprotic Acid Solutions as a Function of pH

Polyprotic acids of the type H2M constitute two ionizable protons. As a result, on titration with a base, they exhibit two equivalence points in the titration curve. During titration, the species H2M, HM−, and M2− will be present in the solution at different points. The fractions of H2M, HM−, and M2− present at the various instances of the titration are denoted by α0, α1, and α2, respectively.
A graph with the alpha values is plotted against the volume of base added during titration. Here, a...

Titration of Polyprotic Acids with a Strong Base

Titration of Polyprotic Acids with a Strong Base

Titration of a polyprotic acid, which contains multiple ionizable protons, involves distinct dissociation steps, each with its own dissociation constant (Ka). Each successive Ka is weaker than the previous one. In the titration of a polyprotic acid like sulfurous acid with a strong base such as sodium hydroxide, the base first neutralizes the initial ionizable proton, forming an intermediate species (e.g., hydrogen sulfite ions). This step's titration curve resembles that of a weak monoprotic...

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Related Experiment Video

Updated: Jun 19, 2026

Measurement of H2S in Crude Oil and Crude Oil Headspace Using Multidimensional Gas Chromatography, Deans Switching and Sulfur-selective Detection

Measurement of H₂S in Crude Oil and Crude Oil Headspace Using Multidimensional Gas Chromatography, Deans Switching and Sulfur-selective Detection

Published on: December 10, 2015

Provisional Advisory Levels (PALs) for hydrogen sulfide (H2S).

Thomas Marshall¹, David Dorman, Donald Gardner

¹Toxicology and Hazard Assessment Group, Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA. marshalltc@ornl.gov

Inhalation Toxicology

|October 16, 2009

Summary

Provisional Advisory Levels (PALs) were developed for hydrogen sulfide (H2S) inhalation exposure. These health guidelines address varying toxic effect severities for short-term public exposure scenarios.

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Last Updated: Jun 19, 2026

Measurement of H2S in Crude Oil and Crude Oil Headspace Using Multidimensional Gas Chromatography, Deans Switching and Sulfur-selective Detection

Measurement of H₂S in Crude Oil and Crude Oil Headspace Using Multidimensional Gas Chromatography, Deans Switching and Sulfur-selective Detection

Published on: December 10, 2015

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Seawater Sampling and Collection

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Published on: June 17, 2009

Area of Science:

Environmental Health
Toxicology
Public Health

Background:

Provisional Advisory Levels (PALs) are health-based guidance values for environmental contaminants.
Hydrogen sulfide (H2S) is a gas with potential for widespread environmental release and public exposure.

Purpose of the Study:

To establish Provisional Advisory Levels (PALs) for hydrogen sulfide (H2S) for various exposure durations.
To inform public health risk assessment and management strategies for H2S exposure.

Main Methods:

Utilized a comprehensive database including human experimental studies, worker evaluations, and animal studies.
Applied established toxicological risk assessment methodologies to derive H2S PALs.
Focused on inhalation exposure pathways due to the gaseous nature of H2S.

Main Results:

Established 24-hour inhalation PALs for H2S: PAL 1 = 1.2 ppm, PAL 2 = 7.0 ppm, PAL 3 = 27 ppm.
Derived 30-day and 90-day inhalation PALs: PAL 1 = 0.85 ppm, PAL 2 = 3.0 ppm.
Determined insufficient data for oral exposure PALs and long-term (2-year) inhalation PALs.

Conclusions:

Inhalation PALs for H2S were successfully developed for short-to-medium term exposures.
Lack of oral exposure data precludes drinking water advisories.
Further research is needed to establish long-term inhalation exposure guidelines for H2S.