isomer

1. Chem a compound that exhibits isomerism with one or more other compounds

2. Physics a nuclide that exhibits isomerism with one or more other nuclides

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

isomer

[′ī·sə·mər]

(chemistry)

One of two or more chemical substances having the same elementary percentage composition and molecular weight but differing in structure, and therefore in properties; there are many ways in which such structural differences occur; one example is provided by the compounds n-butane, CH₃(CH₂)₂CH₃, and isobutane, CH₃CH(CH₃)₂.

(nuclear physics)

One of two or more nuclides having the same mass number and atomic number, but existing for measurable times in different quantum states with different energies and radioactive properties. Also known as nuclear isomer.

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References in periodicals archive

There was a minor shift in retention time for four standard isomers of tocopherol (T) and tocotrienols (T3) when run at different time and resulted in a different of retention time due to variation in temperature and pressure during runs.

Supercritical fluid extraction of vitamin E from de-proteinised natural rubber (DPNR) serum

To further explore the structural characters of the COX-1/COX-2-alpha-Patchouli alcohol isomer complexes, molecular docking, molecular dynamics simulations, and MM-PBSA (molecular mechanical and poisson born/surface accessible) binding-free-energy calculations were performed on COX-1 and COX-2 systems in complexes with alpha-Patchouli alcohol isomers (CID442384, CID521903, CID6432585, CID3080622, CID10955174, and CID56928117).

Binding energy calculation of Patchouli alcohol isomer cyclooxygenase complexes suggested as COX-1/COX-2 selective inhibitor

Indeed, increase in concentration results in transformation of isomer II to isomer I in solutions of 1 and 2 (Figure 5).

Effect of concentration on isomerization of rhodanine derivatives of merocyanine dyes in polar solvents

Solutions of compounds (2a-c) are colorless that confirms presence of only spirocyclic isomer under basic conditions.

Theoretical and experimental study of new photochromic bis-spiropyrans with hydroxyethyl and carboxyethyl substituents

Easy separation of the isomers was achieved by chromatography over silica gel (Scheme 1).

Catalytic synthesis of pyrano- and furoquinolines using nano silica chromic acid at room temperature

Keywords: HPSAM; Aminophenol isomers; NQS; Aqueous solution.

Simultaneous Spectrophotometric Determination of o-Aminophenol and p-Aminophenol Using H-Point Standard Addition Method -Application to Real Waters

The energy of the most stable isomer was considered as a reference to calculate the relative energy for other relevant isomers.

DFT Studies on the Stereoselective Three-Component Ugi Reaction

Based on our isomer distinction method, we successfully assigned isomer grouping for 3,043 (66%) out of 4,610 post-TIC-peak-review suspect peaks.

A Suspect Screening Method for Characterizing Multiple Chemical Exposures among a Demographically Diverse Population of Pregnant Women in San Francisco

Briefly, this approach allowed the discrimination and identification of (1) diCQA positional isomers, (2) CQA glycosides positional isomers, and (3) isobaric compounds, diCQAs and CQA glycosides, in a single chromatographic run, albeit the developed MRM transition parameters were automatically optimized using the positional isomer 3,5-diCQA.

Synchronized Survey Scan Approach Allows for Efficient Discrimination of Isomeric and Isobaric Compounds during LC-MS/MS Analyses

Quality control samples were prepared at three different nominal concentrations: 0.05, 4.1, and 12.4 [micro]g/mL for the cis isomer; 0.028, 0.445, and 1.33 [micro]g/mL for the trans isomer.

Development and Validation of an HPLC-MS/MS Method for Rapid Simultaneous Determination of Cefprozil Diastereomers in Human Plasma

Khaled et al., "Modeling ignition of a heptane isomer: improved thermodynamics, reaction pathways, kinetics, and rate rule optimizations for 2-methylhexane," The Journal of Physical Chemistry A, vol.

Review of Oxidation of Gasoline Surrogates and Its Components