Question

Alcohols are very useful starting materials for the production of many different compounds. The following conversions, starting with 1-butanol, can be carried out in two or more steps. Show the steps (reactants/catalysts) you would follow to carry out the conversions, drawing the formula for the organic product in each step. For each step, a major product must be produced. See Exercise 62. (Hint: In the presence of \(\mathrm{H}^{+}\), an alcohol is converted into an alkene and water. This is the exact reverse of the reaction of adding water to an alkene to form an alcohol.) a. 1 -butanol \(\longrightarrow\) butane b. 1-butanol \(\longrightarrow 2\) -butanone

Short answer

a. Conversion of 1-butanol to butane: 1) 1-butanol + \(\mathrm{H}^{+}\) (from H2SO4 or H3PO4) \(\longrightarrow\) 1-butene + H2O 2) 1-butene + H2/Pd/C \(\longrightarrow\) butane b. Conversion of 1-butanol to 2-butanone: 1) 1-butanol + HBr \(\longrightarrow\) 1-bromobutane + H2O 2) 1-bromobutane + CH3COOK (from KOH and ethanoic acid) \(\longrightarrow\) 2-butanone + KBr

Step-by-step solution

Formation of 1-butene from 1-butanol

To convert 1-butanol to 1-butene, we need to use a dehydrating agent. Typically, we can use concentrated sulfuric acid (H2SO4) or concentrated phosphoric acid (H3PO4) as a dehydrating agent with heat applied. In this step: 1-butanol + \(\mathrm{H}^{+}\) (from H2SO4 or H3PO4) \(\longrightarrow\) 1-butene + H2O

Hydrogenation of 1-butene to butane

To convert 1-butene to butane, we need to carry out a hydrogenation reaction, which involves the addition of hydrogen (H2) across the carbon-carbon double bond. This can be achieved using a catalyst like palladium on carbon (Pd/C) or platinum on carbon (Pt/C) under mild temperature and pressure conditions. In this step: 1-butene + H2/Pd/C \(\longrightarrow\) butane b. Conversion of 1-butanol to 2-butanone

Formation of 1-bromobutane from 1-butanol

To convert 1-butanol to 1-bromobutane, we need to utilize a halogenation reaction. We can use hydrobromic acid (HBr) as the halogenating agent. In this reaction: 1-butanol + HBr \(\longrightarrow\) 1-bromobutane + H2O

Formation of 2-butanone from 1-bromobutane

To convert 1-bromobutane to 2-butanone, we can perform a nucleophilic acyl substitution with ethanoic acid. We can use a strong base like potassium hydroxide (KOH) as the nucleophile, and water as the solvent. In this reaction: 1-bromobutane + CH3COOK (from KOH and ethanoic acid) \(\longrightarrow\) 2-butanone + KBr

Key concepts

1-butanol

1-butanol is an alcohol that is commonly used in organic chemistry as a starting material for various conversions. Alcohols are characterized by the hydroxyl group (-OH) attached to a carbon chain.
It has four carbon atoms (hence "butanol"), which contributes to its physical and chemical properties, such as being moderately soluble in water and having a boiling point of about 117 degrees Celsius.
In organic chemistry, 1-butanol can be transformed into numerous different compounds, which makes it a valuable starting material.

• These transformations typically involve reactions like oxidation, reduction, and substitution.
• The presence of the -OH group in 1-butanol is often targeted in these reactions as it can be readily modified or replaced.
  
• For example, 1-butanol can be converted to alkenes through dehydration, or to haloalkanes through substitution reactions.

alkene synthesis

Alkene synthesis is a fundamental process in organic chemistry, particularly important for creating compounds with carbon-carbon double bonds. One common method for producing alkenes like 1-butene from alcohols involves dehydration.
Dehydration is a chemical reaction that involves the removal of water (H2O) from a molecule.
Here’s how it generally works:

• Using concentrated acids such as sulfuric acid (H2SO4) or phosphoric acid (H3PO4), the hydroxyl group (-OH) from the alcohol is protonated, making it a better leaving group.
• Upon heating, the protonated alcohol loses a water molecule, forming a carbocation intermediate.
• This unstable carbocation then sheds a hydrogen atom, leading to the formation of a double bond and producing an alkene.

The choice of acid and temperature conditions are crucial for this reaction, as they can influence the type of alkene produced and the reaction rate.

hydrogenation

Hydrogenation is a key chemical reaction where hydrogen ( H2 ) is added to organic substances, typically converting unsaturated compounds into saturated ones. It is widely used in the chemical industry for enhancing stability and altering physical properties.
Specifically, in transforming 1-butene to butane, hydrogenation takes an alkene, which contains a double bond, and saturates it by adding hydrogen:

• This reaction is often facilitated by metal catalysts like palladium on carbon (Pd/C) or platinum on carbon (Pt/C).
• The process involves breaking the double bond and adding hydrogen atoms directly to the carbon atoms.

Essential Points:

• The catalyst's role is to lower the activation energy and increase the reaction rate, allowing for smoother conversion under milder conditions.
• Hydrogenation is extensively used not only in petrochemicals but also in food industries, where it is used to convert oils into fats.

nucleophilic substitution

Nucleophilic substitution is an essential type of reaction in organic chemistry where a nucleophile replaces a leaving group in a molecule. This process is crucial for converting alcohols to haloalkanes, which can then undergo further reactions.
Here's how it works:

• A nucleophile, typically an ion or molecule with a lone pair of electrons, attacks an electrophilic carbon atom in the substrate.
• For instance, in converting 1-butanol to 1-bromobutane, hydrobromic acid (HBr) provides the bromine ion (Br-) that replaces the hydroxyl group (-OH).
• The leaving group, in this case, water (H2O) is typically removed, resulting in a new compound.

This reaction type is fundamental in organic synthesis as it enables the construction of complex molecules from simpler substances. It is vital in synthetic strategies, including the creation of pharmaceuticals and plastics.