Question

Outline the synthesis from lauric acid \(\left(\mathrm{n}-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{COOH}\right.\), dodec- anoic acid) of the following compounds: (a) 1-bromododecane; (b) tridecanoic acid (C \(_{13}\) acid); (c) 1 -tetradecanol; (d) 1 -dodecene; (e) dodecane; (f) 1-dodecyne; (g) methyl n-decy1 ketone; (h) 2-dodecanol; (i) undecanoic acid; (j) 2 -tetra- decanol; (k) 2 -methy \(1-2\) -tetradecanol.

Short answer

(a) Synthesis of 1-bromododecane from lauric acid: 1. Reduce lauric acid to dodecanol with LiAlH4: \(\mathrm{n}-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{COOH + LiAlH}_{4} \rightarrow \mathrm{n}-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{CH}_{2} \mathrm{OH}\). 2. Convert dodecanol to 1-bromododecane with HBr: \(n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{CH}_{2} \mathrm{OH} + \mathrm{HBr} \rightarrow n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{CH}_{2} \mathrm{Br} + \mathrm{H}_{2}\mathrm{O}\). (b) Synthesis of tridecanoic acid from lauric acid: 1. Convert lauric acid to dodecanoyl chloride with SOCl2: \(n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{COOH} + \mathrm{SOCl}_{2} \rightarrow n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{COCl} + \mathrm{SO}_{2} + \mathrm{HCl}\). 2. Friedel-Crafts acylation with benzene: \(n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{COCl} + \mathrm{C}_{6} \mathrm{H}_{6} \rightarrow n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COCl} + \mathrm{HCl}\). 3. Basic hydrolysis: \(n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COCl} + \mathrm{OH}^{-} \rightarrow n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COOH}\). (c) Synthesis of 1-tetradecanol from lauric acid: 1. Convert lauric acid to dodecanoyl chloride with SOCl2: \(n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{COOH} + \mathrm{SOCl}_{2} \rightarrow n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{COCl} + \mathrm{SO}_{2} + \mathrm{HCl}\). 2. Grignard reaction with EtMgBr: \(n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{COCl} + CH_{3}CH_{2}\mathrm{MgBr} \rightarrow n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{COCH}_{2} \mathrm{CH}_{3} + \mathrm{MgBrCl}\). 3. Reduce the ketone to 1-tetradecanol with NaBH₄: \(n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{COCH}_{2} \mathrm{CH}_{3} + \mathrm{NaBH}_{4} \rightarrow n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{CH}_{2}\mathrm{OH} \mathrm{CH}_{2} \mathrm{CH}_{3}\).

Step-by-step solution

(a) Synthesis of 1-bromododecane from lauric acid

1. Reduce lauric acid to dodecanol Lauric acid can be reduced to a primary alcohol (dodecanol) by reacting it with lithium aluminium hydride (LiAlH4) followed by acid hydrolysis: \(\mathrm{n}-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{COOH} + \mathrm{LiAlH}_{4} \rightarrow \mathrm{n}-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{CH}_{2} \mathrm{OH}\). 2. Convert dodecanol to 1-bromododecane Dodecanol can be converted to 1-bromododecane through an Sₙ2 reaction with hydrobromic acid (HBr): \(n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{CH}_{2} \mathrm{OH} + \mathrm{HBr} \rightarrow n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{CH}_{2} \mathrm{Br} + \mathrm{H}_{2}\mathrm{O}\).

(b) Synthesis of tridecanoic acid from lauric acid

1. Convert lauric acid to its acyl chloride Lauric acid can be converted to dodecanoyl chloride by reacting it with thionyl chloride (SOCl2): \(n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{COOH} + \mathrm{SOCl}_{2} \rightarrow n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{COCl} + \mathrm{SO}_{2} + \mathrm{HCl}\). 2. Convert dodecanoyl chloride to tridecanoic acid Perform a Friedel-Crafts acylation of benzene using dodecanoyl chloride as the acyl group transfer agent and aluminum chloride (AlCl₃) as the catalyst: \(n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{COCl} + \mathrm{C}_{6} \mathrm{H}_{6} \rightarrow n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COCl} + \mathrm{HCl}\). 3. Hydrolyze the acylated benzene Finally, perform a basic hydrolysis to convert the acylated benzene to tridecanoic acid \(n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COCl} + \mathrm{OH}^{-} \rightarrow n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COOH}\).

(c) Synthesis of 1-tetradecanol from lauric acid

1. Convert lauric acid to dodecanoyl chloride Follow the same procedure as in step 1(b): \(n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{COOH} + \mathrm{SOCl}_{2} \rightarrow n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{COCl} + \mathrm{SO}_{2} + \mathrm{HCl}\). 2. Perform Grignard reaction React dodecanoyl chloride with a two-carbon Grignard reagent like ethylmagnesium bromide (EtMgBr) to form a ketone: \(n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{COCl} + CH_{3}CH_{2}\mathrm{MgBr} \rightarrow n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{COCH}_{2} \mathrm{CH}_{3} + \mathrm{MgBrCl}\). 3. Reduce the ketone to 1-tetradecanol Finally, reduce the ketone to 1-tetradecanol using sodium borohydride (NaBH₄): \(n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{COCH}_{2} \mathrm{CH}_{3} + \mathrm{NaBH}_{4} \rightarrow n-\mathrm{C}_{11} \mathrm{H}_{23} \mathrm{CH}_{2}\mathrm{OH} \mathrm{CH}_{2} \mathrm{CH}_{3}\). The remaining syntheses will follow similar reaction pathways and principles. Keep using various synthetic reactions such as reductions, alkylations, hydrolysis, and different reagents to achieve the desired product for each compound.

Key concepts

Lauric Acid

Lauric acid is a saturated fatty acid, characterized by its 12-carbon backbone. It is also known as dodecanoic acid, represented by the molecular formula \( ext{C}_{11} ext{H}_{23} ext{COOH} \). Being a medium-chain fatty acid,lauric acid is found in various natural sources such as coconut oil and palm kernel oil.Lauric acid is well-known in organic synthesis due to its usefulness in creating various chemical compounds. In reaction schemes, lauric acid can undergo a range of transformations. This is largely due to the versatility and reactivity of its carboxylic acid group. Important Properties of Lauric Acid:

• High melting point, around 44 degrees Celsius
• Moderate solubility in polar solvents like alcohols and etherOverall, lauric acid is a valuable reagent in organic synthesis, serving as a precursor for numerous transformations.

Reaction Mechanisms

Understanding reaction mechanisms is essential in organic chemistry. They describe the step-by-step sequence of events at the molecular level that lead to the formation of a product from reactants. For each reaction, knowing the detailed path that leads to product formation is crucial. This helps explain not only the final product but also intermediate species and the transition states. Types of Mechanisms:

• Addition, where compounds are added to a molecule.
• Substitution, which involves exchanging one atom or group of atoms for another.
• Elimination, removing elements from a molecule to form an unsaturated compound. Reaction mechanisms allow chemists to predict the outcome of reactions and design experiments accordingly. By practicing mechanism problem-solving, students gain a deeper understanding of different reaction types and their practical applications. Overall, mastering reaction mechanisms enhances your organic synthesis skills.

Functional Group Transformations

Functional group transformations are central in the synthesis of complex organic molecules. They involve converting one functional group into another, which can drastically change the properties and reactivity of a molecule. Functional group transformations are pivotal in modifying molecules to achieve desired chemical properties or activities. For instance, converting a carboxylic acid to an alcohol can increase solubility or modify biological activity. Common Transformations:

• Reduction of carbonyl groups to alcohols.
• Oxidation of alcohols to aldehydes or ketones.
• Formation of esters from acids and alcohols. These transformations depend on various factors such as the reagent, reaction conditions, and the presence of activating or deactivating groups in the molecule. Understanding the principles of functional group transformations helps in planning synthetic routes for target molecules.

Sₙ2 Reaction

The Sₙ2 reaction, or bimolecular nucleophilic substitution, plays a crucial role in organic synthesis. It involves the direct displacement of a leaving group by a nucleophile. The hallmark of Sₙ2 reactions is the concerted mechanism, where bond formation and bond breaking occur simultaneously. This leads to an inversion of configuration at the chiral center. Key Features of Sₙ2 Reactions:

• Proceeds in a single step without intermediates.
• Faster in polar aprotic solvents due to increased nucleophile reactivity.
• Reaction rate depends on both the concentration of the substrate and the nucleophile. Sₙ2 reactions are widely used in converting alcohols to alkyl halides, among other transformations. Understanding the factors affecting Sₙ2 reactions, such as steric hindrance and nucleophile strength, is crucial for successful synthesis and product yield in organic chemistry.

Friedel-Crafts Acylation

Friedel-Crafts acylation is a key reaction used in organic synthesis for the formationof aromatic ketones by introducing acyl groups into aromatic rings.This process employs a carboxylic acid chloride as an acylating agent and a Lewis acid catalyst, commonly aluminum chloride (\( ext{AlCl}_3 \)). The catalyst generates a more electrophilic acyl compound, enabling it to attack thearomatic system and form the acylated product.Steps in Friedel-Crafts Acylation:

• Formation of the acylium ion (the species that attacks the aromatic ring).
• Nucleophilic attack on the aromatic ring, forming a sigma complex.
• Loss of a proton, restoring aromaticity and forming the acyl ketone product.Friedel-Crafts acylation is a versatile method, providing a direct pathway to extendcarbon chains and introduce carbonyl functionalities into aromatic compounds.By varying the acyl chloride and aromatic substrates, a vast range of products can be synthesized,making this reaction a staple in the toolbox of organic chemists.