see the attached question and out of these 3 comounds, which one is the best dienophile ?

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see the attached question and out of these 3 comounds, which one is the best dienophile ?

**Hydrogenation Heat Liberation in Compound Pairs**

**Question:**
In each of the following pairs of compounds, circle the one which liberates most heat upon hydrogenation? Why?

**Pair a:**
Compound 1: Benzene
Compound 2: Cyclohexene

**Pair b:**
Compound 1: 1,3-Cyclohexadiene
Compound 2: 1,4-Cyclohexadiene

**Explanation:**
- Pair **a** features two compounds, benzene (a six-carbon ring with alternating double bonds) and cyclohexene (a six-carbon ring with one double bond).
  
- Pair **b** showcases two isomers of cyclohexadiene: 1,3-Cyclohexadiene (double bonds at positions 1 and 3) and 1,4-Cyclohexadiene (double bonds at positions 1 and 4).

The hydrogenation process involves the addition of hydrogen (H₂) to these compounds, converting double bonds to single bonds and liberating heat in the process. The amount of heat released is generally more significant for compounds with higher degrees of unsaturation (more double bonds) and less stability. For example, benzene is particularly stable due to aromaticity, whereas cyclohexene, having one double bond, would release more heat upon hydrogenation. Similarly, the stability of the diene will influence the heat of hydrogenation.
Transcribed Image Text:**Hydrogenation Heat Liberation in Compound Pairs** **Question:** In each of the following pairs of compounds, circle the one which liberates most heat upon hydrogenation? Why? **Pair a:** Compound 1: Benzene Compound 2: Cyclohexene **Pair b:** Compound 1: 1,3-Cyclohexadiene Compound 2: 1,4-Cyclohexadiene **Explanation:** - Pair **a** features two compounds, benzene (a six-carbon ring with alternating double bonds) and cyclohexene (a six-carbon ring with one double bond). - Pair **b** showcases two isomers of cyclohexadiene: 1,3-Cyclohexadiene (double bonds at positions 1 and 3) and 1,4-Cyclohexadiene (double bonds at positions 1 and 4). The hydrogenation process involves the addition of hydrogen (H₂) to these compounds, converting double bonds to single bonds and liberating heat in the process. The amount of heat released is generally more significant for compounds with higher degrees of unsaturation (more double bonds) and less stability. For example, benzene is particularly stable due to aromaticity, whereas cyclohexene, having one double bond, would release more heat upon hydrogenation. Similarly, the stability of the diene will influence the heat of hydrogenation.
### Aromatic Ketones: Structural Representation

Aromatic ketones are organic compounds featuring a carbonyl group (C=O) directly bonded to an aromatic ring. Below are three structural representations of different aromatic ketones:

1. **Phenylacetone**  
   ![Phenylacetone](https://vizhub.health.sydney.edu.au/wp-content/pictures/conversions/10038.edges/cyclophorogrin_clear.png)
   - This compound consists of a benzene ring with a carbonyl group (C=O) attached directly to the ring.

2. **Cyclohexanone** 
   ![Cyclohexanone](https://vizhub.health.sydney.edu.au/wp-content/pictures/conversions/10039.edges/cyclophorogrin_clear.png)
   - Here, the carbonyl group (C=O) is attached to a six-membered cyclohexane ring, forming a cyclohexanone.

3. **Acetophenone** 
   ![Acetophenone](https://vizhub.health.sydney.edu.au/wp-content/pictures/conversions/10040.edges/cyclophorogrin_clear.png)
   - This molecule consists of a benzene ring with a carbonyl group (C=O) and an additional methyl group (CH₃) attached to it, resulting in acetophenone.

Each structurally represented molecule is a clear visual depiction of how the carbonyl functional group varies in attachment to either a benzene ring or a cyclohexane ring. Such representations aid in understanding the different structural forms and their nomenclature in aromatic ketones.
Transcribed Image Text:### Aromatic Ketones: Structural Representation Aromatic ketones are organic compounds featuring a carbonyl group (C=O) directly bonded to an aromatic ring. Below are three structural representations of different aromatic ketones: 1. **Phenylacetone** ![Phenylacetone](https://vizhub.health.sydney.edu.au/wp-content/pictures/conversions/10038.edges/cyclophorogrin_clear.png) - This compound consists of a benzene ring with a carbonyl group (C=O) attached directly to the ring. 2. **Cyclohexanone** ![Cyclohexanone](https://vizhub.health.sydney.edu.au/wp-content/pictures/conversions/10039.edges/cyclophorogrin_clear.png) - Here, the carbonyl group (C=O) is attached to a six-membered cyclohexane ring, forming a cyclohexanone. 3. **Acetophenone** ![Acetophenone](https://vizhub.health.sydney.edu.au/wp-content/pictures/conversions/10040.edges/cyclophorogrin_clear.png) - This molecule consists of a benzene ring with a carbonyl group (C=O) and an additional methyl group (CH₃) attached to it, resulting in acetophenone. Each structurally represented molecule is a clear visual depiction of how the carbonyl functional group varies in attachment to either a benzene ring or a cyclohexane ring. Such representations aid in understanding the different structural forms and their nomenclature in aromatic ketones.
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