Question

Show how to convert propene to each of these compounds, using any inorganic reagents as necessary. (a) Propane (b) 1,2-Propanediol (c) 1-Propanol (d) 2-Propanol (e) Propanal (f) Propanone (g) Propanoic acid (h) 1-Bromo-2-propanol (i) 3-Chloropropene (j) \(1,2,3\)-Trichloropropane (k) 1 -Chloropropane (1) 2-Chloropropane (m) 2-Propen-1-ol (n) Propenal

Short answer

Answer: Propene can be converted to various organic compounds following these steps: (a) Propane: Add hydrogen gas (H2) to propene in the presence of a palladium (Pd) catalyst. (b) 1,2-Propanediol: Treat propene with m-chloroperoxybenzoic acid (m-CPBA) to form an epoxide, then hydrolyze it using water (H2O) and an acid catalyst. (c) 1-Propanol: Use borane (BH3) and tetrahydrofuran (THF), then treat with hydrogen peroxide (H2O2) and sodium hydroxide (NaOH) (d) 2-Propanol: Use mercuric acetate [Hg(O2CCH3)2] and water (H2O), then treated with sodium borohydride (NaBH4) (e) Propanal: Use chromyl chloride (CrO2Cl2) in the presence of pyridine. (f) Propanone: Treat propene with ozone (O3), then followed by reduction with zinc (Zn) and acetic acid (CH3COOH). (g) Propanoic acid: Oxidize propanal using potassium permanganate (KMnO4). (h) 1-Bromo-2-propanol: Use the same process as for 2-propanol, then treat with hydrobromic acid (HBr) and use peroxides as a catalyst. (i) 3-Chloropropene: Use N-Chlorosuccinimide (NCS). (j) \(1,2,3\)-Trichloropropane: Add chlorine gas (Cl2) to propene in the presence of ultraviolet (UV) light, then use SCl2 (thionyl chloride) to replace the hydroxy group (OH). (k) 1-Chloropropane: Use the same process as for 1-propanol, then treat with concentrated HCl and ZnCl2. (l) 2-Chloropropane: Use the same process as for 2-propanol, then treat with concentrated HCl and ZnCl2. (m) 2-Propen-1-ol: Use 9-Borabicyclo[3.3.1]nonane (9-BBN) and DMP (Dess-Martin periodinane) on propene to get propanal. Then use DIBAL-H (Diisobutylaluminium hydride) to get 2-propen-1-ol. (n) Propenal: Use Wacker oxidation in which propene reacts with palladium (II) chloride (\(PdCl_2\)) and cupric chloride (\(CuCl_2\)) in water (H2O), followed by air oxidation.

Step-by-step solution

Hydrogenation of propene

Add hydrogen gas (H2) to propene in the presence of a palladium (Pd) catalyst. This will convert propene (C3H6) to propane (C3H8). (b) 1,2-Propanediol

Epoxidation of propene

Treat propene with 1 equivalent of a peroxyacid like m-chloroperoxybenzoic acid (m-CPBA). This forms an epoxide (propylene oxide).

Hydrolysis of propylene oxide

Hydrolyze the propylene oxide using water (H2O) and acid catalyst to get 1,2-propanediol. (c) 1-Propanol

Hydroboration-oxidation of propene

Using borane (BH3) and tetrahydrofuran (THF), followed by treatment with hydrogen peroxide (H2O2) and sodium hydroxide (NaOH), converts propene to 1-propanol. (d) 2-Propanol

Oxymercuration of propene

Using mercuric acetate [Hg(O2CCH3)2] and water (H2O), followed by treatment with sodium borohydride (NaBH4), converts propene to 2-propanol. (e) Propanal

Partial oxidation of propene

Use a mild oxidizing agent like chromyl chloride (CrO2Cl2) in the presence of pyridine to convert propene to propanal. (f) Propanone

Ozoneolysis of propene

Treat propene with ozone (O3) and then followed by reduction using zinc (Zn) and acetic acid (CH3COOH) to get propanone. (g) Propanoic acid

Oxidation of propanal

Oxidize propanal using an oxidizing agent like potassium permanganate (KMnO4) to convert it to propanoic acid. (h) 1-Bromo-2-propanol

Conversion to 2-propanol

Follow the same process as for 2-propanol synthesis in section (d).

Addition of bromine

Treat 2-propanol with hydrobromic acid (HBr) and use peroxides as a catalyst to convert 2-propanol to 1-bromo-2-propanol. (i) 3-Chloropropene

Allylic halogenation

Use N-Chlorosuccinimide (NCS) to chlorinate propene at an allylic position, which is the 3rd carbon, generating 3-chloropropene. (j) \(1,2,3\)-Trichloropropane

Addition of \(Cl_2\) to propene

Add chlorine gas (Cl2) to propene in the presence of ultraviolet (UV) light to produce 1,2-dichloropropanol.

Halogenation of propyl chloride

Use SCl2 (thionyl chloride) to replace the hydroxy group (OH) with chlorine atom to get \(1,2,3\)-trichloropropane. (k) 1-Chloropropane

Hydroboration-oxidation

Follow the same process as for 1-propanol synthesis in section (c).

Conversion to 1-Chloropropane

Treat 1-propanol with concentrated HCl and ZnCl2 to convert it to 1-chloropropane. (1) 2-Chloropropane

Conversion to 2-propanol

Follow the same process as for 2-propanol synthesis in section (d).

Conversion to 2-Chloropropane

Treat 2-propanol with concentrated HCl and ZnCl2 to convert it to 2-chloropropane. (m) 2-Propen-1-ol

Hydroboration-oxidation

Use 9-Borabicyclo[3.3.1]nonane (9-BBN) as the borane source to treat propene to get 1-propanol. Oxidize 1-propanol with DMP (Dess-Martin periodinane) to transform it to propanal.

Reduction of propanal

Treat propanal with DIBAL-H (Diisobutylaluminium hydride) to convert it into 2-propen-1-ol. (n) Propenal

Partial oxidation of propene

Use Wacker oxidation in which propene reacts with palladium (II) chloride (\(PdCl_2\)) and cupric chloride (\(CuCl_2\)) in water (H2O), followed by an air oxidation to convert propene into propenal.

Key concepts

Organic Synthesis Strategies

Organic synthesis strategies in chemistry are methodologies and tactics employed to construct organic compounds from simpler substances. The complexity and diversity of organic molecules require versatile approaches to create desired structures with specific chemical properties.

For example, the step-by-step transformation of propene into various organic compounds demonstrates some of the central strategies in organic synthesis. One such strategy is functional group interconversion, exemplified by converting the double bond in propene to a range of functional groups through reactions like hydroboration-oxidation, oxymercuration, and epoxidation.

Sequence of Reactions

Synthetic routes often involve a sequence of reactions, each chosen for its ability to introduce or transform functional groups without interfering with others already present in the molecule. For instance, propene undergoes hydroboration-oxidation to yield 1-propanol, which can in turn be transformed into 1-chloropropane by treating it with concentrated HCl and ZnCl2, showcasing sequential reactions that methodically build up complexity.

Selectivity and Specificity

Selectivity is crucial in organic synthesis, as it ensures that the desired product is favored over potential side products. Techniques such as the use of specific catalysts, like palladium in hydrogenation, help achieve high selectivity—turning propene into propane with high specificity.

Understanding various organic synthesis strategies aids in mastering the construction of a wide array of molecules, which is a fundamental skill in organic chemistry.

Functional Group Interconversion

Functional group interconversion (FGI) is a core concept in organic chemistry that involves converting one functional group into another. This process is essential for constructing a complex molecule from a simpler one by systematically changing its chemical functionalities.

The Role of Reagents

In the context of propene conversions, different reagents play pivotal roles in facilitating FGIs. For example, the treatment of propene with m-CPBA leads to epoxidation, introducing an epoxide functional group. Similarly, the conversion of propene to 2-propanol and subsequent treatment with HBr results in a FGI to produce 1-bromo-2-propanol—a process demonstrating the importance of reagent choice in the transformation of functional groups.

Site Selectivity

Besides the type of functional group, the position where transformation occurs is significant. Chemists can achieve site selectivity by exploiting differences in reactivity within a molecule. An allylic halogenation using NCS selectively chlorinates propene at the third carbon, illustrating how deliberate reagent selection determines the outcome of FGI.

Oxidation and Reduction in Organic Chemistry

Oxidation and reduction reactions are vital in organic chemistry for altering the oxidation state of carbon atoms within organic molecules. These reactions can significantly change the chemical properties of a substance.

Oxidizing Agents

Choosing appropriate oxidizing agents allows chemists to control the extent and outcome of oxidation. For instance, treating propene with chromyl chloride provides propanal through a controlled partial oxidation. On the other hand, stronger oxidizers like potassium permanganate or ozone can fully oxidize a molecule, leading to carboxylic acids or ketones as seen in the formation of propanoic acid from propanal and propanone from propene, respectively.

Reductive Agents

Conversely, reducing agents have the ability to add electrons to a molecule, thereby reducing its oxidation state. Sodium borohydride is a common reducing agent used in converting propene into 2-propanol. The choice of reducing agent and reaction conditions determines the specific hydrogenation and reduction pathways, allowing the synthesis of a wide range of alcohols and other reduced forms of organic molecules.