Question

Synthesize butyric acid from any organic compound, using inorganic reagents.

Short answer

To synthesize butyric acid from 1-butene, follow these steps: 1. Convert 1-butene to 1-butanol via hydroboration-oxidation reaction using borane (BH3), hydrogen peroxide (H2O2), and sodium hydroxide (NaOH). \[ C_4H_8 + BH_3 \rightarrow C_4H_9-BH_2 \] \[ C_4H_9-BH_2 + H_2O_2 + NaOH \rightarrow C_4H_10O + NaB(OH)_4 \] 2. Convert 1-butanol to butyraldehyde using controlled oxidation with potassium permanganate (KMnO4) and sulfuric acid (H2SO4) as the catalyst. \[ C_4H_{10}O + KMnO_4 + H_2SO_4 \rightarrow C_4H_8O + KHSO_4 + MnSO_4 + H_2O \] 3. Convert butyraldehyde to butyric acid via complete oxidation using potassium dichromate (K2Cr2O7) and sulfuric acid (H2SO4). \[ C_4H_8O + K_2Cr_2O_7 + H_2SO_4 \rightarrow C_4H_8O_2 + K_2SO_4 + Cr_2(SO_4)_3 + H_2O \]

Step-by-step solution

Convert 1-butene to 1-butanol

First, we will need to convert the 1-butene (C4H8) into 1-butanol (C4H10O). This can be achieved by the hydroboration-oxidation reaction using inorganic reagents. In this reaction, we need borane (BH3) as a hydroborating agent, and hydrogen peroxide (H2O2) and sodium hydroxide (NaOH) as oxidizing agents. The reaction proceeds in two steps: 1. Hydroboration: 1-butene reacts with borane (BH3) to form a trialkylborane intermediate. \[ C_4H_8 + BH_3 \rightarrow C_4H_9-BH_2 \] 2. Oxidation: The trialkylborane intermediate reacts with hydrogen peroxide (H2O2) and sodium hydroxide (NaOH) to form 1-butanol. \[ C_4H_9-BH_2 + H_2O_2 + NaOH \rightarrow C_4H_10O + NaB(OH)_4 \]

Convert 1-butanol to butyraldehyde

Next, we need to convert 1-butanol (C4H10O) into butyraldehyde (C4H8O). This can be done via oxidation using an inorganic oxidizing agent. In this case, we will use potassium permanganate (KMnO4) as the oxidizing agent and sulfuric acid (H2SO4) as the catalyst in a controlled oxidation reaction. The oxidation reaction can be represented as follows: \[ C_4H_{10}O + KMnO_4 + H_2SO_4 \rightarrow C_4H_8O + KHSO_4 + MnSO_4 + H_2O \]

Convert butyraldehyde to butyric acid

Finally, we need to convert butyraldehyde (C4H8O) into butyric acid (C4H8O2). This can also be done via oxidation using inorganic reagents. We will use potassium dichromate (K2Cr2O7) as the oxidizing agent and sulfuric acid (H2SO4) as the catalyst in a complete oxidation reaction. The oxidation reaction can be represented as follows: \[ C_4H_8O + K_2Cr_2O_7 + H_2SO_4 \rightarrow C_4H_8O_2 + K_2SO_4 + Cr_2(SO_4)_3 + H_2O \] In conclusion, butyric acid can be synthesized from 1-butene using a series of reactions involving inorganic reagents such as borane (BH3), hydrogen peroxide (H2O2), sodium hydroxide (NaOH), potassium permanganate (KMnO4), sulfuric acid (H2SO4), and potassium dichromate (K2Cr2O7).

Key concepts

Hydroboration-Oxidation Reaction

Understanding the hydroboration-oxidation reaction is crucial for students learning about functional group interconversion in organic chemistry. This two-step process efficiently converts alkenes into alcohols and is particularly notable for its anti-Markovnikov selectivity—meaning the hydrogen from the borane reagent adds to the more substituted carbon of the alkene.

In the first step, called hydroboration, an alkene undergoes a concerted reaction with borane (BH3), resulting in a trialkylborane intermediate. A hallmark of this step is its stereospecificity; the boron adds to the least hindered face of the double bond almost exclusively in a syn addition. Plus, the reactants take on a triangular transition state, adhering to the rules of concerted reactions. In the second step known as oxidation, this intermediate is then treated with hydrogen peroxide (H2O2) and sodium hydroxide (NaOH) to ultimately yield an alcohol. The beauty of this reaction is in its simplicity and mild conditions, which preserve other sensitive functional groups. Students should note that the order of reagents is irreversible - hydroboration precedes oxidation without exception. To drive the concept home, here's how 1-butene transforms to 1-butanol: In the lab setting, securing pure borane can be a challenge due to its reactivity. Hence, it's more common to use a borane complex, such as BH3·THF, which has a longer shelf life and is easier to handle.

Organic Compound Conversion

Organic compound conversion is a cornerstone of synthetic organic chemistry and involves transforming one organic molecule into another with different functional groups. Such transformations require an understanding of chemical reactivity and selectivity, and often several steps to reach the target molecule. In converting 1-butene to butyric acid, we see an example of systematic functional group modification. The overarching strategy involves adding functional groups to a molecule (functionalization), transforming existing functional groups (functional group interconversion), or increasing the carbon chain length (carbon-carbon bond formation). Each step typically involves a different reagent and reaction condition that must be carefully chosen to progress from reactants to products while minimizing unwanted side reactions.

Building upon the hydroboration-oxidation reaction to produce 1-butanol from 1-butene, we move forward by oxidizing the alcohol to the corresponding aldehyde, butyraldehyde. Controlled oxidation is critical here to prevent overoxidation to the carboxylic acid. Finally, the aldehyde undergoes further oxidation to yield the desired butyric acid. This illustrates the stepwise logic often employed in organic synthesis—each move is like a finely calculated chess game.

Oxidation Reactions in Organic Chemistry

Oxidation reactions are pivotal in organic chemistry, enabling the transformation of a molecule by increasing the number of bonds to oxygen... or removing hydrogen. Such reactions are widely applied in laboratory synthesis and industrial processes. In organic synthesis, oxidation can be used to convert alcohols to aldehydes, ketones, or carboxylic acids. The nature of the oxidizing agent and reaction conditions dictate the outcome. Potassium permanganate (KMnO4) and potassium dichromate (K2Cr2O7) are two strong oxidants often used. However, safety concerns and environmental impact are associated with chromium-based reagents, prompting a shift towards greener alternatives in recent years. The controlled oxidation of 1-butanol to butyraldehyde using KMnO4 requires careful monitoring to stop the reaction at the aldehyde stage. Overoxidation can lead to the formation of the carboxylic acid, which is not the desired outcome in this step. Completing the conversion of butyraldehyde to butyric acid, a more powerful oxidizing mixture of K2Cr2O7 and H2SO4 is used, pushing the reaction to full oxidation.

Students should appreciate the subtleties involved in choosing oxidizing agents. Factors such as reaction temperature, solvent, and stoichiometry play a key role in achieving high yields and purity. It's a balancing act—using just enough reagent to effect change but not so much as to push the reaction too far. Remember, the devil is in the details when it comes to oxidation in organic chemistry.