A GC–MS Analysis of an SN2 Reaction for the Organic Laboratory

Clennan, Malgorzata M.; Clennan, Edward L.

doi:10.1021/ed082p1676

Cited by 8 publications

(9 citation statements)

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“…The experiment is designed to provide students with an appreciation of the power of GC−MS to sort out the details of complex reactions (Scheme ) and to simultaneously illustrate the elimination reactions of alcohols as well as reinforce the fundamental chemistry of carbocations (solvolysis, hydride and alkyl shifts) presented in lecture. The early introduction of mass spectrometry into the curriculum is consistent with the “gradualism” approach suggested by Heldrich and co-workers for the introduction of spectroscopy and by Clennan for GC−MS analysis …”

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confidence: 66%

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Dehydration of Methylcyclohexanol Isomers in the Undergraduate Organic Laboratory and Product Analysis by Gas Chromatography−Mass Spectroscopy (GC−MS)

Clennan

2011

J. Chem. Educ.

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Dehydrations of cis- and trans-2-methylcyclohexanol mixtures were carried out with 60% sulfuric acid at 78−80 °C as a function of time and the products were identified by gas chromatography−mass spectroscopy (GC−MS) analysis. The compounds identified in the reaction mixtures include alkenes, 1-, 3-, and 4-methylcyclohexenes and 1-ethylcyclopentene, as well as the alcohols, 1-, 3-, and 4-methylcyclohexanols, and residual starting material. Independent reactions under identical conditions of the pure cis- and trans-2-methylcyclohexanol isomers, 1-, 3- and 4-methylcyclohexanol were also carried out. These reactions reveal that the cis-isomer reacts predominately to form 1-methylcyclohexene whereas the trans-isomer reacts to give a complicated mixture consisting of the isomeric 1-, 3-, and 4-methylcyclohexanols, 1-, 3-, and 4-methylcyclohexenes, and the ring contraction product, 1-ethylcyclopentene. In the experiment, each student carries out a dehydration of the cis- and trans-2-methylcyclohexanol mixture or of one of the pure isomers and the results from the GC−MS analyses of the whole class are pooled. The analysis reinforces lecture material and provides an appreciation of the complexity of elimination−dehydration reactions that proceed via carbocation intermediates and can undergo intricate rearrangements such as hydride and alkyl shifts. The reaction procedure is straightforward and the GC−MS analysis simple enough so it can easily be used in the first semester of undergraduate organic chemistry laboratory.

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confidence: 66%

“…The early introduction of mass spectrometry into the curriculum is consistent with the "gradualism" approach suggested by Heldrich and co-workers 5 for the introduction of spectroscopy and by Clennan for GC-MS analysis. 6…”

mentioning

confidence: 99%

Dehydration of Methylcyclohexanol Isomers in the Undergraduate Organic Laboratory and Product Analysis by Gas Chromatography−Mass Spectroscopy (GC−MS)

Clennan

2011

J. Chem. Educ.

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“…Small alkyl halides are especially suitable for teaching S N 1 and S N 2 reaction mechanisms in both the lecture and laboratory. In the laboratory, the order of reactivity for S N 2 can be demonstrated by way of the Finkelstein reaction (KI or NaI in acetone at room temperature) using 1°, 2°, and 3° alkyl halides (Supporting Information, p S13). However, it is not so easy to demonstrate the order of reactivity for S N 1.…”

Section: Introductionmentioning

confidence: 99%

Unimolecular Nucleophilic Substitution (S_N1): Structural Reactivity Evidenced by Colored Acid–Base Indicators

et al. 2018

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The different reactivities between 1°, 2°, and 3° butyl chlorides by the unimolecular nucleophilic substitution (SN1) mechanism were easily observed at 60 °C by a solvolysis reaction in ethanol with ether formation. The hydrogen ion from the byproduct HCl reacted with an acid–base indicator such as methyl red to induce a color change. At room temperature, the addition of AgNO3 was used to detect the released chloride ion by AgCl precipitation. The reactivity order (3° > 2° ≫1°) was visually confirmed by both a color change in an indicator and precipitate formation by these safe, quick, and easy assays.

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“…Learning objectives for this experiment include sample injection techniques, quantification of xylitol using GC–MS, and a comparison of external versus internal standard techniques while allowing students to explore a topic that has direct impact on animal safety. Previous undergraduate laboratory experiments have been developed which utilize GC–MS to analyze and quantify components of diverse samples including gasoline, plasticizers, food, water, urine, perfume, beverages, and others. − GC–MS experiments have also been utilized within the organic chemistry curriculum, since it provides a great opportunity for students to analyze organic reactions such as nucleophilic substitution and elimination reactions . This experiment is designed for upper-level undergraduate students enrolled in organic or instrumental analysis courses.…”

Section: Introductionmentioning

confidence: 99%

Determination of Xylitol in Sugar-Free Gum by GC–MS with Direct Aqueous Injection: A Laboratory Experiment for Chemistry Students

et al. 2018

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Proficiency with instrumental analysis via GC–MS is an important skill for chemistry students. The application of analytical techniques and fundamental theoretical principles to real-world problems can be valuable learning exercises for undergraduates which can also improve their analytical thinking skills. Xylitol is generally considered safe for human consumption and is frequently used in sugar-free gum; however, it is extremely toxic to dogs. In this laboratory experiment, upper-level undergraduate chemistry students extract xylitol from both fresh and chewed gum sticks followed by direct aqueous injection GC–MS analysis. Students learn the proper steps and techniques required for sample extraction and preparation and GC–MS analysis, and they determine concentrations of xylitol present in gum samples. Identification and quantification of the chemical components in gum extract occurs via GC–MS analysis; however, other GC detectors could be used. Students also compare external and internal standard calibration methods for xylitol quantification. Upon quantification of xylitol in chewed and unchewed gum samples, students are able to calculate the level of hazard for dogs upon ingestion.

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A GC–MS Analysis of an SN2 Reaction for the Organic Laboratory

Cited by 8 publications

References 1 publication

Dehydration of Methylcyclohexanol Isomers in the Undergraduate Organic Laboratory and Product Analysis by Gas Chromatography−Mass Spectroscopy (GC−MS)

Dehydration of Methylcyclohexanol Isomers in the Undergraduate Organic Laboratory and Product Analysis by Gas Chromatography−Mass Spectroscopy (GC−MS)

Unimolecular Nucleophilic Substitution (S_N1): Structural Reactivity Evidenced by Colored Acid–Base Indicators

Determination of Xylitol in Sugar-Free Gum by GC–MS with Direct Aqueous Injection: A Laboratory Experiment for Chemistry Students

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A GC–MS Analysis of an SN2 Reaction for the Organic Laboratory

Cited by 8 publications

References 1 publication

Dehydration of Methylcyclohexanol Isomers in the Undergraduate Organic Laboratory and Product Analysis by Gas Chromatography−Mass Spectroscopy (GC−MS)

Dehydration of Methylcyclohexanol Isomers in the Undergraduate Organic Laboratory and Product Analysis by Gas Chromatography−Mass Spectroscopy (GC−MS)

Unimolecular Nucleophilic Substitution (SN1): Structural Reactivity Evidenced by Colored Acid–Base Indicators

Determination of Xylitol in Sugar-Free Gum by GC–MS with Direct Aqueous Injection: A Laboratory Experiment for Chemistry Students

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Unimolecular Nucleophilic Substitution (S_N1): Structural Reactivity Evidenced by Colored Acid–Base Indicators