The mass spectrum of n-octane shows a prominent molecular ion peak (m>z 114). There is also a large peak at m>z 57,but it is not the base peak. The mass spectrum of 3,4-dimethylhexane shows a smaller molecular ion, and the peak atmass 57 is the base peak. Explain these trends in abundance of the molecular ions and the ions at mass 57, and predict theintensities of the peaks at masses 57 and 114 in the spectrum of 2,2,3,3-tetramethylbutane.

The mass spectrum of n-octane shows a prominent molecular ion peak (m>z 114). There is also a large peak at m>z 57,but it is not the base peak. The mass spectrum of 3,4-dimethylhexane shows a smaller molecular ion, and the peak atmass 57 is the base peak. Explain these trends in abundance of the molecular ions and the ions at mass 57, and predict theintensities of the peaks at masses 57 and 114 in the spectrum of 2,2,3,3-tetramethylbutane.

Organic Chemistry

8th Edition

ISBN:9781305580350

Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Publisher:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Chapter21: Benzene And The Concept Of Aromaticity

Section: Chapter Questions

Problem 21.20P

See similar textbooks

Similar questions

Following is the mass spectrum of an unknown compound. The two highest peaks are at m/z 120 and 122. Suggest a structure for this compound. (Data from http://webbook.nist.gov/chemistry/.)
The mass spectrum (a) and the infrared spectrum (b) of an unknown hydrocarbon are shown. Propose as many structures as you can.
Long-range coupling between protons more than two carbon atoms apart is sometimes observed when bonds intervene. An example is found in 1-methoxy-l-buten-3-yne. Not only does the acetylenic proton, Î—a, couple with the vinylic proton Hb, it also couples with the vinylic proton Hc, four carbon atoms away. The data are: Construct tree diagrams that account for the observed splitting patterns of Î—a, Hb, and Hc.
The mass spectrum (a) and the infrared spectrum (b) of another unknown hydrocarbon are shown. Propose as many structures as you can.
The mass spectrum of 2,3-dimethylpentane [(CH3)2CHCH(CH3)CH2CH3]shows fragments at m/z = 85 and 71. Propose possible structures for theions that give rise to these peaks.
The mass spectrum of 2,3-dimethylpentane shows peaks at m/z = 57 and 43. Propose possible structures for the ions that give rise to these peaks
2,3-Dimethylbutane and 2,2-dimethylbutane have the same molecular ion in the mass spectrum, but only one of these isomers gives a significant fragment at m/z = 57. (a) Which isomer shows an intense peak at m/z = 57? (b) Propose a structure for the ion that gives rise to this peak. (c) The base peak in the mass spectrum of the other isomer occurs at m/z = 43. What ion gives rise to this peak?
Propylbenzene, C6H5CH2CH2CH3, and isopropyl benzene, C6H5CH(CH3)2, are constitutional isomers with the molecular formula C9H12. One of these compounds shows prominent peaks in its mass spectrum at m/z 120 and 105. The other shows prominent peaks at m/z 120 and 91. Which compound has which spectrum?
The mass spectrum of 1-ethyl-1-methylcyclohexane shows many fragments, with two in very large abundance. One appears at m/z = 111 and the other appears at m/z = 97. Determine the identity and structure of each of these fragments
The mass spectrum of 2,2-dimethylpropane shows only a very weak molecular ion peak at m/z = 72. However, a large peak at m/z = 57 is seen. Suggest a possible structure of the fragment giving rise to this large peak and suggest a reason as to why this peak is so large.
The mass spectrum of 1-ethyl-1-methylcyclohexane shows many fragments, with two in very large abundance. Kne appears af m/z=111 and the other appears at m/z=97. Identify the structure of each of these fragments.
The molecular ion in the mass spectrum of 2-methyl-1-pentene appears at m/z 84. Propose structural formulas for the prominent peaks at m/z 69, 55, 41, and 29.