100% de satisfacción garantizada Inmediatamente disponible después del pago Tanto en línea como en PDF No estas atado a nada
logo-home
Buscado previamente por ti
Buscado previamente por ti
logo
Topic 7 - Modern Analytical Techniques I - Revision Notes 2015 3,70 €
Añadir al carrito
Navegar rápidamente a
Vista previa
  2.  
  3. Pearson (PEARSON)
  4.  
  5. Chemistry 2015
  6.  
  7. Unit 7 - Modern Analytical Techniques I

Notas de lectura

Topic 7 - Modern Analytical Techniques I - Revision Notes 2015

1 revisar
 1 veces vendidas
  • Grado
  • Unit 7 - Modern Analytical Techniques I
  • Institución
  • Pearson (PEARSON)

A comprehensive in-depth, specification led, revision booklet of the 2015 spec chemistry AS level course. Written during AS studies by an AS student, meaning it is written in an easily comprehensible stance for any student wishing to find extra resources to revise from.

Vista previa 2 fuera de 5  páginas

Información del documento

  • 4 de septiembre de 2016
  • 5
  • 2015/2016
  • Notas de lectura
  • Desconocido
  • Todas las clases

Temas

  • edexcel
  • 2015 spec
  • new spec
  • chemistry
  • topic 7
  • chapter 7
  • analytics
  • modern analytical techniques
  • edexcel a level chemistry revision notes

Escuela, estudio y materia

  • A/AS Level
  • Pearson (PEARSON)
  • Chemistry 2015
  • Unit 7 - Modern Analytical Techniques I
Todos documentos para esta materia (1)

1  revisar

review-writer-avatar

Por: jeffreywenwen • 7 año hace

Vendedor

avatar-seller
acook99

Comentarios recibidos

Vista previa del contenido

A Cook 2016
Chapter 7 - Mass Spec in Organic Compounds

Topic 7A: Mass spectrometry

1. Be able to use data from a mass spectrometer to:
i Determine the relative molecular mass of an organic compound from the
molecular ion peak
ii Suggest possible structures of a simple organic compound from the m/z of the molecular
ion and fragmentation patterns

Background to mass spectrometry

The mass spectrum of an element often appears as very simple, with small vertical lines, called
peaks, each representing a different isotope of the element

In contrast, the masse spectrum of an organic compound often appears complex, with a large
number of peaks. If all the peaks are included,m there may be more peaks than there are atoms in
a molecule of the compound, so something different is happening.

The molecular Ion peak

The peak furthest to the right with the highest (m/z) value, is the molecular ion peak. This peak is
the molecular ion peak - the result of the organic molecule losing an electron in the mass
spectrometer.

The equation for this process, using butane as an example is:

C4H10 + e- —> C4H10+ + 2e-

An electron collides with a butane molecule and knocks out an electron, so forming a positive ion
form the molecule. The m/z value of this peak (58) indicates the relative molecule mass of butane.

Other peaks

The spectrum may show a very small peak to the right of the molecular ion peak (M+1 peak).
Caused by the presence of naturally occurring isotope (13C instead of the normal 12C) in the
molecule. Approximately 99% of all carbon atoms are 12C, with the remaining 1% being 13C.

The peaks with smaller m/z values, are a result of the fragmentation in the mass spectrometer,
rearrangement reactions and the loss of more than one electron.

Fragmentation in hydrocarbons:

Fragmentation is very common, and can be used to work out the structure of an organic
compound:

Consider the breaking of a carbon-carbon bond, in the molecular ion formed from a hydrocarbon.
Two species are formed. They are:

1. Another positive ion
2. A neutral species (usually a radical)

Examples of fragmentation

A very simple example of fragmentation is the molecular ion of ethane, which can fragment to form
a methyl cation and a methyl radical:

, A Cook 2016
(CH3-CH3)+ —> CH3+ + CH3

The ethane molecule is symmetrical, and there is only one carbon-carbon bond. So the second
methyl group is just as likely to become a positive ion, as the left one was. This would be the
equation for that to happen:

(CH3-CH3)+ —> CH3 + CH3+

You can see that the products produced are identical so there will be a peak at m/z = 15.

Sometimes there is a radical formed which is shown the a dot (representing the unpaired electron),
and the molecular ion is shown with a dot as well as a positive charge, as in this example:


(CH3-CH3)+. —> CH3. + CH3+

Now consider propene’s fragmentation:

There are 2 carbon - carbon bonds, but their are equivalent - they can both be described as the
bond between the central carbon and one of the two terminal carbons. However, there are now two
possible fragment ions the can form:

(CH3-CH2-CH3)+ —> CH3+ + CH2-CH3

(CH3-CH2-CH3)+ —> CH3 + (CH2-CH3)+

You would therefore see peaks at m/z = 15 (methyl) and m/z = 29 (ethyl) in its spectrum.

Radicals are not detected in a mass spectrometer so only the positive ions will be detected.

Mass spectrum

The peak with the largest m/z value is the molecular ion peak - caused by the organic molecule
losing one electron in the mass spec. It is the molecular mass of the compound too.

The peak which is the highest is called the base peak and is caused by the ion which has the
highest abundance

Los beneficios de comprar resúmenes en Stuvia estan en línea:

Garantiza la calidad de los comentarios

Garantiza la calidad de los comentarios

Compradores de Stuvia evaluaron más de 700.000 resúmenes. Así estas seguro que compras los mejores documentos!

Compra fácil y rápido

Compra fácil y rápido

Puedes pagar rápidamente y en una vez con iDeal, tarjeta de crédito o con tu crédito de Stuvia. Sin tener que hacerte miembro.

Enfócate en lo más importante

Enfócate en lo más importante

Tus compañeros escriben los resúmenes. Por eso tienes la seguridad que tienes un resumen actual y confiable. Así llegas a la conclusión rapidamente!

Preguntas frecuentes

What do I get when I buy this document?

You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.

100% de satisfacción garantizada: ¿Cómo funciona?

Nuestra garantía de satisfacción le asegura que siempre encontrará un documento de estudio a tu medida. Tu rellenas un formulario y nuestro equipo de atención al cliente se encarga del resto.

Who am I buying this summary from?

Stuvia is a marketplace, so you are not buying this document from us, but from seller acook99. Stuvia facilitates payment to the seller.

Will I be stuck with a subscription?

No, you only buy this summary for 3,70 €. You're not tied to anything after your purchase.

Can Stuvia be trusted?

4.6 stars on Google & Trustpilot (+1000 reviews)

45,681 summaries were sold in the last 30 days

Founded in 2010, the go-to place to buy summaries for 15 years now

Empieza a vender

Vistos recientemente

Resumen ·

(97)

Volledige samenvatting Basisboek Online Marketing 4e druk

Examen ·

(0)

FL CAM Practice Exam #1 Questions and Answers 100% Accurate

Resumen ·

(2)

Engels in het basisonderwijs - Samenvatting hoofdstuk 6 t/m 9

Examen ·

(0)

NYU Admissions Ambassador Questions with Accurate Answers

Examen ·

(0)

Intermediate Accounting Exam Questions Answered Correctly

Examen ·

(0)

FISDAP AIRWAY MID EAST EXAM WITH 100% CORRECT ANSWERS 2024

Examen ·

(0)

Illinois Aquatics Pesticide License questions and answers

Examen ·

(0)

UTA A&P II EXAM 3 STUDY QUESTIONS WITH CORRECT ANSWERS

Resumen ·

(0)

Subject-Verb-Agreement explained in a 1o-min-presentation

3,70 €  1x  vendido
  • (1)
Añadir al carrito
Añadido