The reaction of ( Z )-2-pentene with water and a trace of H 2 SO 4 forms two products. Identify the products from their mass spectra. <IMAGE>

Hello, everyone. Let's work through this problem together. It says acid catalyzed hydration of two hexen produces two distinct alcohols, identify the products and match each with the correct mass spectrum. So we have our two mass spectra and our four answer choices list our two distinct alcohols respective to mass spectrum. One and mass spectrum two. So answer choice A says two hexen and three hexen. B says one hexen and two hexen C says three hexen and two hexen. D says three hexen and one hexen. So let's draw our reactant to hexen and determine what the two products will be. So we have a six carbon chain, 123456 with an alkene, a double bond between carbons two and three. Now this is acid catalyzed hydration. So we are reacting with water and an acid and we are going to create an alcohol group right on either side of that double bond. So that means we will have an alcohol group on carbon number two, which gives us two hexen and an alcohol group on carbon three, which gives us three hexen. So we know our products are two hexen and three hexen which means we can eliminate answer choices B and D. So now we just have to determine which mass spectrum relates to which product. So, since our products are alcohols, right? Alcohols, we don't expect the molecular ion peak to appear in the mass spectrum, right? Alcohols are going to commonly fragment and one of the most common fragmentation patterns is an alpha cleavage. So let's look at what fragments would be produced if we perform an alpha cleavage on these two products. So first looking at two hexen, we have our radical cat ion and we want to cleave between the alpha carbon and the carbon that has the alcohol group. Right? So mhm We will have the radical that is on the alcohol come down to form a double bond. And it does that by meeting with one of the electrons from that carbon carbon bond that carbon alpha carbon bond and we will create a new radical on that alpha carbon. So we've created our double bond to our alcohol, which is our radical or sorry, our cat ion fragment and then we have ch two ch two ch two ch three, which is our radical. So our ion fragment has an M over Z of 45. Now, if we look at our spectra, we see that spectrum one has that large base peak with M over Z 45. So that means spectrum one is going to be 42 hexen. And that makes answer choice a the correct answer. Let's double check for three hexen and make sure that the fragmentation aligns with the spectrum given to us. So for three hexen notice that there are a couple peaks that have a larger intensity. So we are going to have a couple common fragmentation. So we can do the alpha cleavage to the left hand carbon or the right hand carbon. So let's start with the right hand carbon in this case, which creates a fragment. A cat ion fragment M over Z 59. And we have our radical CH two ch two ch three or we could fragment with the other alpha carbon to form CH three ch two radical and CH three ch two ch two ch double bonded to oh which is our cat ion fragment. And that has an M over Z of 73. So if we go to mass spectrum number two, we see those larger intensity base peaks 73 and 59 M over Z. So that confirms that mass spectrum two is 43 hexen. So once again, our correct answer is a with spectrum one representing two hexen, spectrum two, representing three hexen. That's it for this one. I hope this was helpful and thanks for watching.

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1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

15. Analytical Techniques:IR, NMR, Mass Spect

Mass Spect:Fragmentation

Organic Chemistry

15. Analytical Techniques:IR, NMR, Mass Spect

Mass Spect:Fragmentation

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Problem 18

Textbook Question

The reaction of (Z)-2-pentene with water and a trace of H₂SO₄ forms two products. Identify the products from their mass spectra.
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Verified step by step guidance

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.

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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.

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.

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.

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