Question

Show reagents and experimental conditions to synthesize the following compounds from 1-propanol (any derivative of 1-propanol prepared in one part of this problem may be used for the synthesis of another part of the problem). (a) Propanal (b) Propanoic acid (c) Propene (d) 2-Propanol (e) 2-Bromopropane (f) 1-Chloropropane (g) 1,2-Dibromopropane (h) Propyne (i) 2-Propanone (j) 1-Chloro-2-propanol (k) Methyloxirane (1) Dipropyl ether (m) Isopropyl propyl ether (n) 1-Mercapto-2-propanol (o) 1-Amino-2-propanol (p) 1,2-Propanediol

Short answer

(d) 2-Propanol #tag_title#Step 1: Reduction of 2-propanone to 2-propanol #tag_content#To synthesize 2-propanol from 1-propanol, we first need to prepare 2-propanone using the steps outlined for (i) 2-Propanone. Once 2-propanone is obtained, carry out a reduction reaction using sodium borohydride (NaBH4) in a suitable solvent, such as methanol (MeOH). The reaction proceeds as follows: 2-propanone + NaBH4 → 2-propanol + NaBH3 (e) 2-Bromopropane #tag_title#Step 1: Substitution of 2-propanol to 2-bromopropane #tag_content#First, prepare 2-propanol using the steps outlined for (d) 2-Propanol. Then, to synthesize 2-bromopropane from 2-propanol, we need to perform a substitution reaction using hydrobromic acid (HBr) in water as the solvent. The reaction proceeds as follows: 2-propanol + HBr → 2-bromopropane + water

Step-by-step solution

Oxidation of 1-propanol

To synthesize propanal from 1-propanol, we need to oxidize 1-propanol using an appropriate oxidizing agent. A suitable oxidizing agent is pyridinium chlorochromate (PCC) in dichloromethane as a solvent. The reaction occurs as follows: 1-propanol + PCC → propanal + reduced PCC (b) Propanoic acid

Oxidation of 1-propanol to propanal

As mentioned in part (a), oxidize 1-propanol using pyridinium chlorochromate (PCC) to obtain propanal.

Oxidation of propanal to propanoic acid

To convert propanal to propanoic acid, we need to further oxidize it. Use potassium permanganate (KMnO4) in an aqueous solution and heat the reaction mixture to achieve this transformation. The reaction proceeds as follows: propanal + KMnO4 → propanoic acid + reduced KMnO4 (c) Propene

Dehydration of 1-propanol to propene

To synthesize propene from 1-propanol, we need to dehydrate 1-propanol. To do this, heat 1-propanol in the presence of concentrated sulfuric acid (H2SO4) and distill the reaction products to isolate propene formed as a gas. The reaction proceeds as follows: 1-propanol + H2SO4 → propene + water For the rest of the steps, please refer to the reactions and reagents identified in Phase 1. These will guide you in constructing the appropriate step-by-step synthesis for each target molecule, as illustrated in the examples provided for (a), (b), and (c).

Key concepts

Oxidation Reactions

Oxidation reactions are a cornerstone in organic synthesis, particularly when it comes to transforming alcohols into more complex compounds. An oxidation reaction involves the loss of electrons from a molecule, which often results in the increase of oxygen content or the loss of hydrogen. In the case of alcohols, oxidation can lead to the formation of aldehydes, ketones, or carboxylic acids.

Using 1-propanol as a starting material, we observed its oxidation to form propanal by employing pyridinium chlorochromate (PCC), an efficient oxidizing agent. PCC selectively converts primary alcohols like 1-propanol to aldehydes like propanal, without further oxidation to carboxylic acids.

For complete oxidation to propanoic acid, the aldehyde propanal is further oxidized using a stronger oxidizing agent, like potassium permanganate (KMnO4), in an aqueous solution. This showcases the two-step oxidation where PCC and KMnO4 play crucial roles.

Dehydration Reactions

Dehydration reactions involve the removal of water (H2O) from a molecule, which is an essential transformation in organic chemistry. In the context of alcohols, dehydration is used to convert alcohols to alkenes by eliminating water.

For instance, to convert 1-propanol to propene, a dehydration reaction is required. This process involves heating the 1-propanol in the presence of a strong acid like concentrated sulfuric acid (H2SO4). The acid acts as a catalyst, promoting the removal of the hydroxyl group along with a hydrogen atom from a neighboring carbon atom, resulting in the formation of an alkene, in this case, propene.

These reactions are typically carried out under controlled conditions to carefully manage the temperature and prevent side reactions.

Alcohol Transformations

Transforming alcohols into a variety of other organic compounds is a fundamental aspect of synthetic organic chemistry. Alcohols can undergo numerous chemical reactions, facilitating the synthesis of a wide array of products.

One example of alcohol transformation is the conversion of 1-propanol into different functional compounds such as alkenes, ethers, and esters. Dehydration and oxidation are two primary methods through which these transformations occur.

For example, 1-propanol can be converted into 2-propanol, a secondary alcohol, which is often achieved through catalytic hydrogenation or rearrangement reactions. This highlights the versatility of alcohols as precursors in synthetic pathways.

Synthetic Pathways

Creating synthetic pathways involves planning and carrying out a series of chemical reactions to transform a starting material into a desired product. This is both an art and a science, requiring knowledge of reagent properties, reaction mechanisms, and process conditions.

Starting with 1-propanol, a multitude of target molecules can be synthesized through carefully crafted pathways. Consider the stepwise oxidation and dehydration reactions that covert 1-propanol into propanal, propanoic acid, or propene. Each pathway employs specific reagents and conditions, leading to different outcomes.

Synthesizing complex molecules often requires multi-step processes, combining reactions such as oxidation, dehydration, and substitution, underscoring the intricacies of designing synthetic pathways.

Reagents and Conditions

In organic synthesis, the choice of reagents and the conditions under which reactions are performed determine the success and outcome of the transformations. The correct selection leads to efficiently converting starting materials to the desired products.

For oxidizing 1-propanol to propanal, PCC in dichloromethane provides a mild condition favoring selective oxidation. For further oxidation to propanoic acid, KMnO4 in an aqueous medium with heat ensures complete oxidation.

Dehydrating 1-propanol to propene necessitates concentrated sulfuric acid, which acts as both a catalyst and a dehydrating agent. Understanding these factors allows chemists to design efficient synthetic strategies and troubleshoot any reaction challenges.