HOME PAGE * KS3 SCIENCES * GCSE BIOLOGY CHEMISTRY PHYSICS * ADVANCED LEVEL CHEMISTRY

SPECTROSCOPY INDEXES  *  All Advanced Organic Chemistry Notes  *  [SEARCH BOX]

Advanced Organic Chemistry: Mass spectrum of 2,3-dimethylpentane

The mass spectrum of 2,3-dimethylpentane

Doc Brown's Chemistry Advanced Level Pre-University Chemistry Revision Study Notes for UK IB KS5 A/AS GCE advanced A level organic chemistry students US K12 grade 11 grade 12 organic chemistry courses involving molecular spectroscopy analysing mass spectra of 2,3-dimethylpentane

See also comparing the 1H NMR and 13C NMR spectra of the nine alkane structural isomers of C7H16

C7H16 mass spectrum of 2,3-dimethylpentane fragmentation pattern of m/z m/e ions for analysis and identification of 2,3-dimethylpentane image diagram doc brown's advanced organic chemistry revision notes 

2,3-dimethylpentane C7H16 alkanes structure and naming (c) doc b alkanes structure and naming (c) doc b alkanes structure and naming (c) doc b

For more see The molecular structure, classification and naming of alkanes

Interpreting the fragmentation pattern of the mass spectrum of 2,3-dimethylpentane

[M]+ is the molecular ion peak (M) with an m/z of 100 corresponding to [C7H16]+, the original 2,3-dimethylpentane molecule minus an electron, [(CH3)2CHCH(CH3)CH2CH3]+.

The tiny M+1 peak at m/z 101, corresponds to an ionised 2,3-dimethylpentane molecule with one 13C atom in it i.e. an ionised 2,3-dimethylpentane molecule of formula [13C12C6H16]+

Carbon-13 only accounts for ~1% of all carbon atoms (12C ~99%), but the more carbon atoms in the molecule, the greater the probability of observing this 13C M+1 peak.

2,3-dimethylpentane has 7 carbon atoms, so on average, ~1 in 14 molecules will contain a 13C atom.

This sort of argument also applies to fragment ions from the parent molecular ion of 2,3-dimethylpentane - though the ratio will be greater:

e.g. m/z 44 ion could be [13C12C2H7]+, m/z 58 ion [13C12C3H9]+, and m/z 72 ion [13C12C4H11]+

These ions might be more likely than those containing only 12C isotope atoms

i.e. [C3H8]+, [C4H10]+ and [C5H12]+

Either way, for identification purposes, all these peaks add uniqueness to the fragmentation pattern of the mass spectrum of 2,3-dimethylpentane.

The most abundant ion of the molecule under mass spectrometry investigation (2,3-dimethylpentane) is usually given an arbitrary abundance value of 100, called the base ion peak, and all other abundances ('intensities') are measured against it.

Identifying the species giving the most prominent peaks (apart from M) in the fragmentation pattern of 2,3-dimethylpentane.

Unless otherwise indicated, assume the carbon atoms in heptane are the 12C isotope.

Some of the possible positive ions, [molecular fragment]+, formed in the mass spectrometry of 2,3-dimethylpentane.

The parent molecular ion of 2,3-dimethylpentane m/z 100: [C7H16]+

Identifying the species giving the most prominent peaks (apart from M) in the fragmentation pattern of 2,3-dimethylpentane.

m/z value of [fragment]+ 85 71 70 57 56 55
[molecular fragment]+ [C6H13]+ [C5H11]+ [C5H10]+ [C4H9]+ [C4H8]+ [C4H7]+
m/z value of [fragment]+ 43 42 41 39 29 27
[molecular fragment]+ [C3H7]+ [C3H6]+ [C3H5]+ [C3H3]+ [C2H5]+ [C2H3]+

Analysing and explaining the principal ions in the fragmentation pattern of the mass spectrum of 2,3-dimethylpentane

Examples of equations to explain some of the most abundant ion peaks in the mass spectrum of 2,3-dimethylpentane

Atomic masses: H = 1;  C = 12 (13 for ~1 in 100)

Bond enthalpies = kJ/mol: C-C = 348;  C-H = 412

Most fragmentation in alkanes arises from C-C bond scission (C-C bond weaker than C-H bond).

Formation of m/z 85 ion:

[(CH3)2CHCH(CH3)CH2CH3]+  ===>  [C6H13]+  +  CH3

C-C bond fission in the parent molecular ion of 2,3-dimethylpentane.

Here a methyl group is broken off, mass change = 100 - 15 = 81.

Formation of m/z 71 ion:

[(CH3)2CHCH(CH3)CH2CH3]+  ===>  [(CH3)2CHCHCH3]+  +  CH2CH3

C-C bond fission in the parent molecular ion of 2,3-dimethylpentane.

Here an end ethyl group is broken off, mass change = 100 - 29 = 71.

Formation of m/z 57 ion:

[(CH3)2CHCH(CH3)CH2CH3]+  ===>  [CH3CHCH2CH3]+  +  CH3CHCH3

C-C bond fission in the parent molecular ion of 2,3-dimethylpentane.

Loss of a CH3CHCH3 group, mass change = 100 - 43 = 57.

The m/z 57 ion intensity is not as high as the base peak ion of m/z 43 and the almost equally high m/z 56 ion.

Formation of m/z 56 ion:

[(CH3)2CHCHCH3]+  ===>  [C4H8]+  +  CH3

C-C bond fission in the m/z 71 ion, loss of methyl group, mass change = 71 - 15 = 56.

The m/z 56 ion intensity is nearly as high as the base peak ion of m/z 43 ion.

Formation of m/z 43 ion:

[(CH3)2CHCH(CH3)CH2CH3]+  ===>  [CH3CHCH3]+  +  C4H9

C-C bond fission in the parent molecular ion of 2,3-dimethylpentane.

Loss of a C4H9 group, mass change = 100 - 57 = 43, a secondary carbocation.

Ethene is often eliminated to give a smaller fragment e.g. the m/z 71 ion gives the m/z 43 ion.

[C5H11]+  ===>  [C3H7]+  +  C2H4

Mass change 71 - 28 = 43.

Formation of m/z 29 ion:

[(CH3)2CHCH(CH3)CH2CH3]+  ===>  [CH2CH3]+  +  C5H11

C-C bond fission in the parent molecular ion of 2,3-dimethylpentane.

Here an end ethyl group is broken off, mass change = 100 - 71 = 29.

Comparing the 1H NMR and 13C NMR spectra of the nine alkane structural isomers of C7H16

You can distinguish all 9 isomers from a data combination of their number of 1H NMR chemical shifts,

and their resulting integrated 1H proton ratios, plus, their number of 13C chemical shifts.

Name of the alkane structural isomer of molecular formula C7H16 Abbreviated structural formulae of the nine isomers of molecular formula C7H16 (interpretation complications with 3-methylhexane and 2,3-dimethylpentane because they exhibit R/S isomerism due to a chiral carbon) Skeletal formula of the nine alkane isomers of  molecular formula C7H16 Number of 1H NMR chemical shifts (δ) and proton ratio (links to spectrum) Number of 13C chemical shifts (δ) (links to spectrum)
heptane structural formula skeletal formula alkanes molecular structure naming (c) doc b heptane skeletal formula alkanes molecular structure naming (c) doc b 4 δ: proton ratio: 3:2:2:1 (6:4:4:2 in the molecule) 4 δ shifts
2-methylhexane structural formula skeletal formula alkanes molecular structure naming (c) doc b 2-methylhexane skeletal formula alkanes molecular structure naming (c) doc b 6 δ: proton ratio : 6:3:2:2:2:1 6 δ shifts
3-methylhexane structural formula skeletal formula alkanes molecular structure naming (c) doc b 3-methylhexane skeletal formula alkanes molecular structure naming (c) doc b 7 δ: proton ratio: 3:3:3:2:2:2:1 (simplification) !!! 7 δ shifts
3-ethylpentane structural formula skeletal formula alkanes molecular structure naming (c) doc b 3-ethylpentane skeletal formula alkanes molecular structure naming (c) doc b 3 δ: proton ratio: 9:6:1 3 δ shifts
2,2-dimethylpentane structural formula skeletal formula alkanes molecular structure naming (c) doc b 2,2-dimethylpentane skeletal formula alkanes molecular structure naming (c) doc b 4 δ: proton ratio: 9:3:2:2 5 δ shifts
2,3-dimethylpentane structural formula skeletal formula alkanes molecular structure naming (c) doc b 2,3-dimethylpentane skeletal formula alkanes molecular structure naming (c) doc b 6 δ: proton ratio: 6:3:3:2:1:1 (simplification) !!! 6 δ shifts (simplification) !!!
2,4-dimethylpentane structural formula skeletal formula alkanes molecular structure naming (c) doc b 2,4-dimethylpentane skeletal formula alkanes molecular structure naming (c) doc b 3 δ: proton ratio: 12:2:2 3 δ shifts
3,3-dimethylpentane structural formula skeletal formula alkanes molecular structure naming (c) doc b 3,3-dimethylpentane skeletal formula alkanes molecular structure naming (c) doc b 3 δ: proton ratio: 3:3:2 (6:4:4 in the molecule) 4 δ shifts
2,2,3-trimethylbutane structural formula skeletal formula alkanes molecular structure naming (c) doc b 2,2,3-trimethylbutane skeletal formula alkanes molecular structure naming (c) doc b 3 δ: proton ratio: 9:6:1 4 δ shifts

Key words & phrases: C7H16 image diagram on how to interpret and explain the mass spectrum of 2,3-dimethylpentane m/z m/e base peaks, image and diagram of the mass spectrum of 2,3-dimethylpentane, details of the mass spectroscopy of 2,3-dimethylpentane,  low and high resolution mass spectrum of 2,3-dimethylpentane, prominent m/z peaks in the mass spectrum of 2,3-dimethylpentane, comparative mass spectra of 2,3-dimethylpentane, the molecular ion peak in the mass spectrum of 2,3-dimethylpentane, analysing and understanding the fragmentation pattern of the mass spectrum of 2,3-dimethylpentane, characteristic pattern of peaks in the mass spectrum of 2,3-dimethylpentane, relative abundance of mass ion peaks in the mass spectrum of 2,3-dimethylpentane, revising the mass spectrum of 2,3-dimethylpentane, revision of mass spectroscopy of 2,3-dimethylpentane, most abundant ions in the mass spectrum of 2,3-dimethylpentane, how to construct the mass spectrum diagram for abundance of fragmentation ions in the mass spectrum of 2,3-dimethylpentane, how to analyse the mass spectrum of 2,3-dimethylpentane, how to describe explain the formation of fragmented ions in the mass spectra of 2,3-dimethylpentane equations for explaining the formation of the positive ions in the fragmentation of the ionised molecule of 2,3-dimethylpentane recognising the base ion peak of 2,3-dimethylpentane interpreting interpretation the mass spectrum of 2,3-dimethylpentane (CH3)2CHCH(CH3)CH2CH3

Stick diagram of the relative abundance of ionised fragments in the fingerprint pattern of the mass spectrum of 2,3-dimethylpentane. Table of the m/e m/z values and formula of the ionised fragments in the mass spectrum of 2,3-dimethylpentane. The m/e m/z value of the molecular ion peak in the mass spectrum of 2,3-dimethylpentane.  The m/e m/z value of the base ion peak in the mass spectrum of 2,3-dimethylpentane. Possible examples of equations showing the formation of the ionised fragments in 2,3-dimethylpentane. Revision notes on the mass spectrum of 2,3-dimethylpentane. Matching and deducing the structure of the 2,3-dimethylpentane molecule from its mass spectrum. Mass spectroscopy of aliphatic alkanes, mass spectra of 2,3-dimethylpentane, a structural isomer of molecular formula C7H16


Links associated with 2,3-dimethylpentane

The chemistry of ALKANES revision notes INDEX

Mass spectroscopy index

ALL SPECTROSCOPY INDEXES

All Advanced Organic Chemistry Notes

Use My Google search site box

Email doc b: chem55555@hotmail.com

TOP OF PAGE

Infrared spectra of the isomers of C7H16

The infrared spectrum of heptane

The infrared spectrum of 2-methylhexane

The infrared spectrum of 3-methylhexane

The infrared spectrum of 3-ethylpentane

The infrared spectrum of 2,2-dimethylpentane

The infrared spectrum of 2,3-dimethylpentane

The infrared spectrum of 2,4-dimethylpentane

The infrared spectrum of 3,3-dimethylpentane

The infrared spectrum of 2,2,3-trimethylbutane

Mass spectra of the isomers of C7H16

The mass spectrum of heptane

The mass spectrum of 2-methylhexane

The mass spectrum of 3-methylhexane

The mass spectrum of 3-ethylpentane

The mass spectrum of 2,2-dimethylpentane

The mass spectrum of 2,3-dimethylpentane

The mass spectrum of 2,4-dimethylpentane

The mass spectrum of 3,3-dimethylpentane

The mass spectrum of 2,2,3-trimethylbutane

H-1 proton NMR spectra of ALKANES

1H NMR spectra of the isomers of C7H16

The H-1 NMR spectrum of heptane

The H-1 NMR spectrum of 2-methylhexane

The H-1 NMR spectrum of 3-methylhexane

The H-1 NMR spectrum of 3-ethylpentane

The H-1 NMR spectrum of 2,2-dimethylpentane

The H-1 NMR spectrum of 2,3-dimethylpentane

The H-1 NMR spectrum of 2,4-dimethylpentane

The H-1 NMR spectrum of 3,3-dimethylpentane

The H-1 NMR spectrum of 2,2,3-trimethylbutane

C-13 carbon-13 NMR spectra of ALKANES

13C NMR spectra of the isomers of C7H16

The C-13 NMR spectrum of heptane

The C-13 NMR spectrum of 2-methylhexane

The C-13 NMR spectrum of 3-methylhexane

The C-13 NMR spectrum of 3-ethylpentane

The C-13 NMR spectrum of 2,2-dimethylpentane

The C-13 NMR spectrum of 2,3-dimethylpentane

The C-13 NMR spectrum of 2,4-dimethylpentane

The C-13 NMR spectrum of 3,3-dimethylpentane

The C-13 NMR spectrum of 2,2,3-trimethylbutane

 Doc Brown's Chemistry 

*

TOP OF PAGE

latest video game release mass spectrum of 2,3-dimethylpentane latest pop music releases mass spectrum of 2,3-dimethylpentane download free music mass spectrum of 2,3-dimethylpentane latest film releases mass spectrum of 2,3-dimethylpentane latest high street fashion in clothes mass spectrum of 2,3-dimethylpentane fashionable trending in clothing mass spectrum of 2,3-dimethylpentane girls buy clothes mass spectrum of 2,3-dimethylpentane spend a lot of money on clothes mass spectrum of 2,3-dimethylpentane shoes mass spectrum of 2,3-dimethylpentane sweets and chocolates mass spectrum of 2,3-dimethylpentane magazines and make-up. Boys buy food and drink mass spectrum of 2,3-dimethylpentane computer games mass spectrum of 2,3-dimethylpentane DVDs and CDs mass spectrum of 2,3-dimethylpentane girls and boys spend a lot of money on credit for mobile phones mass spectrum of 2,3-dimethylpentane buses and trains to transport them going out. Girls spend a lot of money on clothes color colour preferences in clothes mass spectrum of 2,3-dimethylpentane cool sunglasses mass spectrum of 2,3-dimethylpentane boys  buy expensive things like designer sports clothes and trainers mass spectrum of 2,3-dimethylpentane teenagers save for holidays mass spectrum of 2,3-dimethylpentane clothes mass spectrum of 2,3-dimethylpentane mobile phones mass spectrum of 2,3-dimethylpentane birthday presents and electronic goods mass spectrum of 2,3-dimethylpentane teenage accessories mass spectrum of 2,3-dimethylpentane Favourite style of jeans. A typical girl’s shopping list includes mobile phone credit deals mass spectrum of 2,3-dimethylpentane fashionable quality cool airpods mass spectrum of 2,3-dimethylpentane air pods mass spectrum of 2,3-dimethylpentane fashionable clothes mass spectrum of 2,3-dimethylpentane the most popular favourite sneakers mass spectrum of 2,3-dimethylpentane fancy shoes mass spectrum of 2,3-dimethylpentane sweets mass spectrum of 2,3-dimethylpentane chocolates mass spectrum of 2,3-dimethylpentane magazines mass spectrum of 2,3-dimethylpentane lip moisturizer  mass spectrum of 2,3-dimethylpentane lots on make-up mass spectrum of 2,3-dimethylpentane well being mass spectrum of 2,3-dimethylpentane teenage decor decorating their room mass spectrum of 2,3-dimethylpentane teenagers like LED string lantern lights mass spectrum of 2,3-dimethylpentane beauty products for teenagers mass spectrum of 2,3-dimethylpentane denim jackets mass spectrum of 2,3-dimethylpentane scrunchies coolness mass spectrum of 2,3-dimethylpentane fashionable back packs mass spectrum of 2,3-dimethylpentane typical boy’s shopping list includes mobile credit deals mass spectrum of 2,3-dimethylpentane eating out takeaway food and drinks mass spectrum of 2,3-dimethylpentane what teenagers like to buy in clothes mass spectrum of 2,3-dimethylpentane computer games mass spectrum of 2,3-dimethylpentane DVDs mass spectrum of 2,3-dimethylpentane CDs mass spectrum of 2,3-dimethylpentane what teenagers talk about mass spectrum of 2,3-dimethylpentane what teenagers worry about mass spectrum of 2,3-dimethylpentane what teenagers like to do for fun sports mass spectrum of 2,3-dimethylpentane what cool things do teenagers buy mass spectrum of 2,3-dimethylpentane resale websites like eBay Teenager education word cloud how do I apply to university to study biology? mass spectrum of 2,3-dimethylpentane what courses are available at university to study biology? mass spectrum of 2,3-dimethylpentane what grades do I need to get to university to study biology? mass spectrum of 2,3-dimethylpentane how do I apply to university to study chemistry? mass spectrum of 2,3-dimethylpentane what courses are available at university to study chemistry? mass spectrum of 2,3-dimethylpentane what grades do I need to get to university to study chemistry? mass spectrum of 2,3-dimethylpentane how do I apply to university to study physics? mass spectrum of 2,3-dimethylpentane what courses are available at university to study physics? mass spectrum of 2,3-dimethylpentane what grades do I need to get to university to study physics? mass spectrum of 2,3-dimethylpentane how do I apply to university to study biomedical sciences? mass spectrum of 2,3-dimethylpentane what courses are available at university to study biomedical sciences? mass spectrum of 2,3-dimethylpentane what grades do I need to get to university to study biomedical sciences mass spectrum of 2,3-dimethylpentane how do I apply to university to study medicine? mass spectrum of 2,3-dimethylpentane what courses are available at university to study medicine? mass spectrum of 2,3-dimethylpentane what grades do I need to get to university to study medicine? mass spectrum of 2,3-dimethylpentane how do I apply to university to study biochemistry? mass spectrum of 2,3-dimethylpentane what courses are available at university to study biochemistry? mass spectrum of 2,3-dimethylpentane what grades do I need to get to university to study biochemistry? mass spectrum of 2,3-dimethylpentane how do I apply to university to study mathematics? mass spectrum of 2,3-dimethylpentane what courses are available at university to study mathematics? mass spectrum of 2,3-dimethylpentane what grades do I need to get to university to study mathematics? mass spectrum of 2,3-dimethylpentane how do I apply to university to study chemical engineering? mass spectrum of 2,3-dimethylpentane what courses are available at university to study chemical engineering? mass spectrum of 2,3-dimethylpentane what grades do I need to get to university to study chemical engineering? mass spectrum of 2,3-dimethylpentane how do I apply to university to study civil engineering? mass spectrum of 2,3-dimethylpentane what courses are available at university to study civil engineering? mass spectrum of 2,3-dimethylpentane what grades do I need to get to university to study civil engineering? mass spectrum of 2,3-dimethylpentane how do I apply to university to study electrical engineering? mass spectrum of 2,3-dimethylpentane what courses are available at university to study electrical engineering? mass spectrum of 2,3-dimethylpentane what grades do I need to get to university to study electrical engineering? mass spectrum of 2,3-dimethylpentane how do I apply to university to study computer science? mass spectrum of 2,3-dimethylpentane what courses are available at university to study computer science? mass spectrum of 2,3-dimethylpentane what grades do I need to get to university to study computer science? mass spectrum of 2,3-dimethylpentane