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Ch. 14 - Ethers, Epoxides, and Thioethers
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
All textbooksWade 9th EditionCh. 14 - Ethers, Epoxides, and ThioethersProblem 7
Chapter 14, Problem 7

Propose a fragmentation to account for each numbered peak in the mass spectrum of n-butyl isopropyl ether.
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Identify the molecular structure of n-butyl isopropyl ether. It consists of a butyl group (C4H9) attached to an oxygen atom, which is further connected to an isopropyl group (C3H7). The molecular formula is C7H16O.
Understand the process of fragmentation in mass spectrometry. Fragmentation occurs when the molecule is ionized, leading to the breaking of bonds and the formation of smaller ionized fragments. These fragments correspond to the peaks in the mass spectrum.
Propose a fragmentation pathway for the first peak. A common fragmentation involves the cleavage of the bond between the oxygen atom and the butyl group, resulting in a butyl cation (C4H9⁺) and an isopropoxy radical (C3H7O•). The mass of the butyl cation can be calculated as follows: \( \text{C}_4\text{H}_9^+ \) = \( 4(12.01) + 9(1.008) \).
Propose a fragmentation pathway for the second peak. Another possible fragmentation involves the cleavage of the bond between the oxygen atom and the isopropyl group, resulting in an isopropyl cation (C3H7⁺) and a butoxy radical (C4H9O•). The mass of the isopropyl cation can be calculated as follows: \( \text{C}_3\text{H}_7^+ \) = \( 3(12.01) + 7(1.008) \).
Analyze additional peaks by considering secondary fragmentations or rearrangements. For example, the butyl cation (C4H9⁺) can undergo further fragmentation to form smaller ions such as the ethyl cation (C2H5⁺) or propyl cation (C3H7⁺). Similarly, the isopropyl cation (C3H7⁺) can fragment further to form smaller ions. Calculate the masses of these smaller ions to match them with the peaks in the spectrum.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Mass Spectrometry

Mass spectrometry is an analytical technique used to measure the mass-to-charge ratio of ions. It involves ionizing chemical species and sorting the ions based on their mass. The resulting mass spectrum displays peaks corresponding to different ions, where the height of each peak indicates the relative abundance of each ion. Understanding mass spectrometry is crucial for interpreting the fragmentation patterns of compounds.
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How to Read a Mass Spectrum

Fragmentation Patterns

Fragmentation patterns refer to the specific ways in which a molecule breaks apart into smaller ions during mass spectrometry. These patterns are influenced by the molecular structure and the stability of the resulting fragments. Analyzing fragmentation helps in identifying the structure of the original compound, as each peak in the mass spectrum corresponds to a specific fragment formed during ionization.
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n-Butyl Isopropyl Ether Structure

n-Butyl isopropyl ether is an organic compound with a specific structure that influences its fragmentation behavior. It consists of a butyl group (C4H9) and an isopropyl group (C3H7) connected by an ether linkage (R-O-R'). Understanding the molecular structure is essential for predicting how the compound will fragment under ionization, which directly relates to the peaks observed in its mass spectrum.
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Related Practice
Textbook Question

Show how you would use the Williamson ether synthesis to prepare the following ethers. You may use any alcohols or phenols as your organic starting materials.

(d) ethyl n-propyl ether (two ways)

(e) benzyl tert-butyl ether (benzyl = Ph–CH2–)

1235
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Textbook Question

Give a common name (when possible) and a systematic name for each compound.

(d)

(e)

(f)

1117
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Textbook Question

Propose a Williamson synthesis of 3-butoxy-1,1-dimethylcyclohexane from 3,3-dimethyl-cyclohexanol and butan-1-ol.

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Textbook Question

Give a common name (when possible) and a systematic name for each compound.

(a) CH3OCH=CH2

(b) CH3CH2OCH(CH3)2

(c) ClCH2CH2OCH3

1784
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Textbook Question

1,4-Dioxane is made commercially by the acid-catalyzed condensation of an alcohol.

(a) Show what alcohol will undergo condensation, with loss of water, to give 1,4-dioxane.

(b) Propose a mechanism for this reaction.

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Textbook Question

Show how the following ethers might be synthesized using (1) alkoxymercuration– demercuration and (2) the Williamson synthesis. (When one of these methods cannot be used for the given ether, point out why it will not work.)

a. 2-methoxybutane

b. ethyl cyclohexyl ether

c. 1-methoxy-2-methylcyclopentane

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