Skip to main content
Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy
Bruice - Organic Chemistry 8th Edition
Bruice8th EditionOrganic ChemistryISBN: 9780135213711Not the one you use?Change textbook
All textbooksBruice 8th EditionCh. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis SpectroscopyProblem 18
Chapter 14, Problem 18

The reaction of (Z)-2-pentene with water and a trace of H2SO4 forms two products. Identify the products from their mass spectra.
<IMAGE>

Verified step by step guidance
1
Step 1: Recognize the reaction type. The reaction of (Z)-2-pentene with water in the presence of a trace of H2SO4 is an example of an acid-catalyzed hydration reaction. This reaction adds a water molecule (H and OH) across the double bond of the alkene.
Step 2: Determine the regioselectivity of the reaction. According to Markovnikov's rule, the hydrogen atom (H⁺) from water will add to the carbon of the double bond that already has more hydrogen atoms, while the hydroxyl group (OH⁻) will add to the carbon with fewer hydrogen atoms.
Step 3: Analyze the stereochemistry. Since the starting material is (Z)-2-pentene, the addition of water can lead to the formation of two stereoisomers (enantiomers) due to the creation of a new chiral center at the carbon where the OH group is added.
Step 4: Predict the products. The two products will be 2-pentanol, with the hydroxyl group attached to the second carbon. These products will be enantiomers: (R)-2-pentanol and (S)-2-pentanol.
Step 5: Use mass spectrometry to identify the products. The mass spectra of the products will show a molecular ion peak at m/z = 88 (the molecular weight of 2-pentanol). Fragmentation patterns, such as the loss of water (m/z = 70) or alkyl groups, can help confirm the structure of the products.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Was this helpful?

Key Concepts

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

Electrophilic Addition

Electrophilic addition is a fundamental reaction mechanism in organic chemistry where an electrophile reacts with a nucleophile, leading to the formation of a more saturated product. In the case of (Z)-2-pentene reacting with water in the presence of H2SO4, the double bond of the alkene acts as a nucleophile, attacking the electrophilic hydrogen from the acid, facilitating the addition of water across the double bond.
Recommended video:
Guided course
09:23
1,2 vs 1,4 Addition

Markovnikov's Rule

Markovnikov's Rule states that in the addition of HX to an alkene, the hydrogen atom will attach to the carbon with the greater number of hydrogen atoms already attached. This principle helps predict the major product of the reaction between (Z)-2-pentene and water, as the hydroxyl group will preferentially bond to the more substituted carbon, leading to the formation of specific alcohol products.
Recommended video:
Guided course
03:54
The 18 and 16 Electron Rule

Mass Spectrometry

Mass spectrometry is an analytical technique used to measure the mass-to-charge ratio of ions. It provides information about the molecular weight and structure of compounds. In the context of the reaction products from (Z)-2-pentene, mass spectra can help identify the resulting alcohols by analyzing their fragmentation patterns and molecular ions, allowing for the differentiation between the products formed.
Recommended video:
Guided course
01:25
How to Read a Mass Spectrum
Related Practice
Textbook Question

Which occurs at a larger wavenumber:

a. the C–O stretch of phenol or the C–O stretch of cyclohexanol?

b. the C=O stretch of a ketone or the C=O stretch of an amide?

c. the C–N stretch of cyclohexylamine or the C–N stretch of aniline?

3
views
Textbook Question

a. Which occurs at a larger wavenumber:

3. a C–N stretch or a C=N stretch?

4. a C=O stretch or a C–O stretch?

Textbook Question

a. Which occurs at a larger wavenumber:

1. a C=C stretch or a C=C stretch?

2. a C–H stretch or a C–H bend?

1
views
Textbook Question

Using curved arrows, show the principal fragments you would expect to see in the mass spectrum of each of the following compounds:

c.

6
views
Textbook Question

Using curved arrows, show the principal fragments you would expect to see in the mass spectrum of each of the following compounds:

f.

4
views
Textbook Question

Using curved arrows, show the principal fragments you would expect to see in the mass spectrum of each of the following compounds:

d.

2
views