Name: amines in mass spectra: nitrogen rule
Uploaded: 2024-12-05T18:32:20.000Z
Duration: 55 s
Channel: JoVE

Aminler, rezonansla stabilize edilmiş nitrojen içeren bir katyon ve bir alkil radikali elde etmek için kütle spektrometresinde ⍺-bölünmeye uğrar.
Aminler için ilginç bir şekilde, bileşikteki nitrojen atomlarının sayısı, kütle spektrometresinin nitrojen kuralı olarak da adlandırılan moleküler iyonun moleküler ağırlığını etkiler.
Kurala göre, tek sayıda nitrojen atomu içeren nötr bir organik bileşik, tek sayılı moleküler ağırlığa sahip bir moleküler iyon üretecektir.
Örneğin, bir nitrojen atomuna sahip olan trietilaminin kütle spektrumunu düşünün.
Burada, moleküler iyonun tek bir kütle-yük oranı 101'dir.
Moleküler iyonun ⍺-bölünme üzerine parçalanması, bir metil radikalini serbest bırakır ve 86'lık bir kütle-yük oranında bir baz tepe noktası oluşturur.

kütle spektrometrisi: amin parçalanması

Mass Spectrometry: Amine Fragmentation

Aminler, karakteristik parçalanma desenlerine göre kütle spektroskopisi kullanılarak tanımlanabilir. Aminlerin moleküler iyonları ⍺-ayrılması yoluyla parçalanmaya uğrar. Aminlerdeki karbon-karbon bağlarının ⍺-ayrılması, bir alkil radikali ve rezonansla stabilize edilmiş azot içeren katyon üretir.

Aminlerde, azot atomlarının sayısı, kütle spektrometrisinin azot kuralıyla tanımlanan moleküler iyonun kütlesini etkiler. Bu kural, tek veya tek sayıda azot atomu içeren bir bileşiğin tek molekül ağırlığına sahip bir moleküler iyon ürettiğini, azot atomu olmayan veya çift sayıda azot atomu içeren bir bileşiğin ise çift molekül ağırlığına sahip bir moleküler iyon ürettiğini belirtir.

Örneğin, bir nitrojen atomu içeren 3-metil-1-bütanaminin kütle spektrumu, 87'lik tek kütle-yük oranına sahip bir moleküler iyon gösterir. Bu moleküler iyonun ⍺-ayrılması yoluyla parçalanması, 2-metil propil radikalinin kaybına karşılık gelen 30'luk bir kütle-yük oranında bir kütle sinyali içeren bir baz tepesi üretir.

Benzer şekilde, trietilaminin ⍺-ayrılması yoluyla parçalanması, 86'lık bir kütle-yük oranında bir katyon üretir. Aşağıda gösterildiği gibi, moleküler iyon tepesi 101'lik tek bir kütle-yük oranı gösterir.

<img alt="Figure1" src="/files/ftp_upload/13048/13048_PT_Figure_1.svg" style="text-align: center; height: 105px;">

Kütle Spektrometrisi: Amin Parçalanması

Aminler, karakteristik parçalanma modellerine dayalı olarak kütle spektroskopisi kullanılarak tanımlanabilir. Aminlerin moleküler iyonları parçalanmaya uğrar ...

Education

JoVE Core

Analytical Chemistry

Analitik Kimya

Unit 1

Ünite 1

Mass Spectrometry Fragmentation Methods

Kütle Spektrometrisi Parçalanma Yöntemleri

KEY TERMS AND CONCEPTS

TEMEL TERİMLER VE KAVRAMLAR

amines in mass spectra: nitrogen rule

Amines can be identified in mass spectrometry by their fragmentation patterns and by the nitrogen rule. The molecular ions of amines often break apart through β-cleavage, which cuts a carbon-carbon bond next to the nitrogen. This process forms an alkyl radical and a resonance-stabilized nitrogen-containing cation.

The nitrogen rule helps predict the mass of the molecular ion. A compound with one nitrogen atom, or any odd number of nitrogen atoms, gives a molecular ion with an odd molecular weight. A compound with no nitrogen atoms, or an even number of nitrogen atoms, gives a molecular ion with an even molecular weight.

The mass spectrum of 3-methyl-1-butanamine shows this pattern clearly. Because it contains one nitrogen atom, its molecular ion appears at m/z 87, which is odd. Fragmentation by β-cleavage gives a base peak at m/z 30, after loss of the 2-methyl propyl radical.

Triethylamine shows a similar fragmentation pattern. Its molecular ion appears at m/z 101, and β-cleavage produces a cation at m/z 86. These peaks help identify amines by linking molecular ion mass with their characteristic breakdown products.

Amines in Mass Spectra: Nitrogen Rule

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key terms and concepts

Learn how amines fragment in mass spectrometry, how β-cleavage works, and how the nitrogen rule helps predict odd or even molecular ion masses.

Amines in Mass Spectra: Nitrogen Rule | JoVE K12

JoVE Core Analitik Kimya, karmaşık kimyasal prensiplerini anlaşılır, ilgi çekici animasyonlara dönüştürerek basitleştirir ve SI Birimlerinden NMR spektroskopisine kadar konuları daha erişilebilir ve anlaşılır hale getirir. Buna ek olarak, bilim insanlarının yer aldığı videolar, bu kavramların dünya çapındaki laboratuvarlarda yürütülen gerçek dünya araştırmalarındaki uygulamalarını gösterir.

Amines in Mass Spectra: Nitrogen Rule

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