Table of contents

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

13. Alcohols and Carbonyl Compounds

Grignard Reaction

Organic Chemistry

13. Alcohols and Carbonyl Compounds

Grignard Reaction

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5: minutes

Problem 41f

Textbook Question

Show how you would synthesize the following:
f. 2,5-dimethylhexane from a four-carbon alkyl halide

Verified step by step guidance

Step 1: Begin by identifying the target molecule, 2,5-dimethylhexane, and its structural features. It has a six-carbon chain with methyl groups attached at the 2nd and 5th positions. This suggests that the synthesis will involve chain elongation and branching.

Step 2: Choose a suitable four-carbon alkyl halide as the starting material. For example, 1-bromobutane (CH₃CH₂CH₂CH₂Br) can serve as the base structure for chain elongation.

Step 3: Perform a reaction to introduce branching. Use a Grignard reagent, such as methylmagnesium bromide (CH₃MgBr), to add a methyl group to the chain. This reaction will require a carbonyl intermediate, such as butanone (CH₃CH₂COCH₃), which can be synthesized from the alkyl halide.

Step 4: Repeat the process to introduce the second methyl group at the desired position. This can be achieved by converting the intermediate into another carbonyl compound and reacting it with methylmagnesium bromide again.

Step 5: Finally, ensure the product is fully reduced to form the desired alkane, 2,5-dimethylhexane. Use hydrogenation (H₂ with a metal catalyst like Pd/C) to reduce any remaining unsaturated bonds or intermediates to the final alkane structure.

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Key Concepts

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

Alkyl Halides

Alkyl halides are organic compounds containing a carbon chain bonded to a halogen atom (F, Cl, Br, I). They serve as important intermediates in organic synthesis, allowing for the introduction of functional groups through nucleophilic substitution or elimination reactions. Understanding their reactivity is crucial for designing synthetic pathways.

Nucleophilic Substitution Reactions

Nucleophilic substitution reactions involve the replacement of a leaving group (like a halogen) by a nucleophile. These reactions can occur via two main mechanisms: SN1 (unimolecular) and SN2 (bimolecular). The choice of mechanism affects the stereochemistry and rate of the reaction, which is essential for synthesizing specific products like 2,5-dimethylhexane.

Carbon Chain Elongation

Carbon chain elongation is a synthetic strategy used to increase the length of a carbon chain in organic molecules. This can be achieved through various methods, including coupling reactions or the use of alkyl halides in nucleophilic substitution. In the context of synthesizing 2,5-dimethylhexane, understanding how to effectively elongate a four-carbon alkyl halide is key to achieving the desired product.

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Related Practice

Textbook Question

Point out the flaws in the following incorrect Grignard syntheses.

(c)

(d)

Textbook Question

A variety of organometallics, which as strong nucleophiles can react with epoxides, are introduced in Chapter 16. Predict the product of these reactions. [Hint: Assume the carbon–metal bond in each is ionic, with the carbon possessing the negative charge.]

(b)

Textbook Question

Predict the product of the following epoxide addition reactions.

(b)

Textbook Question

Addition to an epoxide occurs via an S_N2 reaction, but the stereochemistry of the epoxide is retained in the following reaction. Why?

Textbook Question

Predict the products of the following reactions.

(a) allyl bromide + cyclohexyl magnesium bromide

Textbook Question

Show how the reaction of an allylic halide with a Grignard reagent might be used to synthesize the following hydrocarbons.

c. 1-cyclopentylpent-2-ene