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

Los alquinos generalmente se fragmentan para formar el catión 3-propinil o el catión propargil, que está estabilizado por resonancia.
Los alquinos pueden ser terminales o internos.
En los alquinos terminales, la señal del catión 3-propinil aparece con una relación masa-carga de 39. En los alquinos internos, el catión 3-propinil es sustituido y aparece en una mayor relación masa-carga.
Otro tipo de fragmentación que se observa con frecuencia es la pérdida del átomo de hidrógeno del carbono alquino terminal que lleva el triple enlace.
Por lo tanto, los alquinos terminales exhiben una señal de masa intensa a una relación masa-carga de 1 u más baja que el ion molecular de la molécula de analito. Este pico se denota como el pico M-1.

espectrometría de masas: fragmentación de alquinos

Mass Spectrometry: Alkyne Fragmentation

La fragmentación de los alquinos se produce preferentemente en el enlace carbono-carbono entre el carbono α y β del enlace alquino para generar un catión 3-propinilo (o catión propargilo). En los alquinos terminales, existe el único tipo de fragmentación que produce el catión 3-propinilo. El catión 3-propinilo no sustituido exhibe un pico en una relación masa-carga de 39. En los alquinos internos, el catión 3-propinilo está sustituido. Por ejemplo, el 2-pentino se fragmenta en el catión 3-propinilo sustituido con metilo, que posteriormente aparece como una señal de masa en la relación masa-carga de 56. El catión 3-propinilo está estabilizado por resonancia y la señal de masa correspondiente es intensa en el espectro de masas de los alquinos. La Figura 1 muestra la fragmentación del 1-pentino en un radical etilo y un catión 3-propinilo estabilizado por resonancia.
<img alt="Figure1" src="/files/ftp_upload/13045/13045-PT_Figure_1.svg" style="height: 115px;">
Figura 1: Fragmentación del ion molecular 1-pentino para producir el catión 3-propinilo.
Otra vía de fragmentación observada en los alquinos terminales es la pérdida de hidrógeno del carbono sp terminal. Esto da como resultado una señal de masa con una relación masa-carga de una unidad menor que la del ion molecular. Este pico M–1 es muy intenso y se convierte en el pico base en los espectros de masa de muchos alquinos, por lo que se puede utilizar para identificarlos.
<img alt="Figure2" src="/files/ftp_upload/13045/13045-PT_Figure_2.svg" style="height: 275px;">
Figura 2: El espectro de masas del 1-pentino.

Espectrometría de masas: fragmentación de alquinos

La fragmentación de los alquinos se produce preferentemente en el enlace carbono-carbono entre el α y β carbono del enlace alquino para generar un ...

Education

Educación

JoVE Core

Analytical Chemistry

Química Analítica

Unit 1

Unidad 1

Mass Spectrometry Fragmentation Methods

Métodos de fragmentación en espectrometría de masas

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

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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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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