Name: alkyne mass spectra and key peaks
Uploaded: 2024-12-05T18:32:20.000Z
Duration: 53 s
Channel: JoVE

炔烃通常会断裂形成3-丙炔基阳离子或丙炔基阳离子，后者具有共振稳定作用。
炔烃可以是端基炔烃或内炔烃。
在末端炔烃中，3-丙炔基阳离子信号出现在质荷比为39处。在内部炔烃中，3-丙炔基阳离子被取代，出现在更高的质荷比处。
另一种常见的裂解是末端炔烃碳原子上氢原子的丢失，该碳原子含有三键。
因此，末端炔烃在质荷比比分析物分子离子低1 u的位置显示出强烈的质谱信号。该峰被称为M–1峰。

质谱法：炔烃碎裂

Mass Spectrometry: Alkyne Fragmentation

炔烃的碎裂会优先发生在炔键的 α 碳和 β 碳之间的碳碳键上，从而生成 3-炔丙基阳离子（或炔丙基阳离子）。在末端炔烃中，只有一种碎裂类型会产生 3-炔丙基阳离子。未被取代的 3-炔丙基阳离子在质荷比为 39 时出现峰值。在内部炔烃中，3-炔丙基阳离子被取代。例如，2-戊炔会碎裂成甲基取代的 3-炔丙基阳离子，随后在质荷比为 56 时作为质量信号出现。3-炔丙基阳离子具有共振稳定性，相应的质量信号在炔烃的质谱中非常强烈。图 1 显示了 1-戊炔碎裂并生产乙基自由基和具有共振稳定性的 3-炔丙基阳离子。

<img alt="Figure1" src="/files/ftp_upload/13045/13045-PT_Figure_1.svg" style="text-align: center; height: 115px;">

 图 1：1-戊炔分子离子碎裂并产生了 3-炔丙基阳离子。


 在末端炔烃中观察到的末端 sp 碳失去氢的过程是另一种碎裂途径。这会导致质量信号的质荷比与分子离子相比来说低一个单位。这个 M-1 峰非常强烈，使其成为了许多炔烃质谱中的基峰，因此可以用于对炔烃进行识别。

<img alt="Figure2" src="/files/ftp_upload/13045/13045-PT_Figure_2.svg" style="text-align: center; height: 275px;">

 图 2：1-戊炔的质谱。

炔烃的断裂优先发生在炔键的α碳与β碳之间的碳-碳键，生成一个……

Education

教育

JoVE Core

Analytical Chemistry

分析化学

Unit 1

第一单元

Mass Spectrometry Fragmentation Methods

质谱碎片化方法

KEY TERMS AND CONCEPTS

关键术语与概念

alkyne mass spectra and key peaks

Alkyne mass spectra often show strong peaks from two main fragmentation paths. One path breaks the carbon-carbon bond between the alpha and beta carbons of the alkyne bond. This produces a 3-propynyl cation, also called a propargyl cation.

In terminal alkynes, this is the only fragmentation path that gives the 3-propynyl cation. The unsubstituted 3-propynyl cation appears at a mass-to-charge ratio of 39. In internal alkynes, the 3-propynyl cation is substituted. For example, 2-pentyne forms a methyl-substituted 3-propynyl cation, which gives a mass signal at m/z 56.

The 3-propynyl cation is resonance-stabilized. That stability makes its signal intense in the mass spectrum of alkynes. A related example is the fragmentation of 1-pentyne, which produces an ethyl radical and a resonance-stabilized 3-propynyl cation.

Terminal alkynes can also lose hydrogen from the terminal sp carbon. This gives a mass signal that is one unit less than the molecular ion. The M-1 peak is often very intense and can become the base peak in many alkyne mass spectra. Because of this, it can help identify alkynes, including 1-pentyne.

Alkyne Mass Spectra and Key Peaks

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mass spectrometry: alkyne fragmentation

Alkyne mass spectra often show strong peaks from two main fragmentation paths. One path breaks the carbon-carbon bond between the alpha and beta carbons of the alkyne bond. This produces a 3-propynyl cation, also called a propargyl cation. In terminal alkynes, this is the only fragmentation path that gives the 3-propynyl cation. The unsubstituted 3-propynyl cation appears at a mass-to-charge ratio of 39. In internal alkynes, the 3-propynyl cation is substituted. For example, 2-pentyne forms a...

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key terms and concepts

Learn how alkynes fragment in mass spectrometry, including the 3-propynyl cation, m/z 39 and 56 peaks, and the strong M-1 peak in terminal alkynes.

Alkyne Mass Spectra and Key Peaks | JoVE K12

analytical chemistry

JoVE Core Analytical Chemistry simplifies complex chemical principles by breaking them down into clear, engaging animations, making topics from SI Units to NMR spectroscopy more accessible and straightforward. Additionally, the scientist-in-action videos highlight the application of these concepts in real-world research conducted in laboratories globally.

Alkyne Mass Spectra and Key Peaks

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