Question

(a) What do ethane and ethanol have in common? (b) How does 1 -propanol differ from propane?

Short answer

(a) Ethane and ethanol both have two carbon atoms bonded to each other with a single bond, and both have a total of six hydrogen atoms. They are both derivatives of the same parent hydrocarbon, ethylene (C2H4). (b) The primary difference between 1-propanol and propane is the presence of a hydroxyl group in 1-propanol (making it an alcohol) while propane is an alkane. Their chemical structures are CH3-CH2-CH2OH and CH3-CH2-CH3, respectively. This difference in functional groups leads to varying physical and chemical properties, such as boiling points, polarity, and reactivity.

Step-by-step solution

Describe the chemical structure of ethane

Ethane is an organic compound with the molecular formula \(C_2H_6\). It consists of two carbon atoms, each connected to three hydrogen atoms, with a single bond between the carbon atoms. The chemical structure can be represented as CH3-CH3 or \(H_3C-CH_3\).

Describe the chemical structure of ethanol

Ethanol is an organic compound with the molecular formula \(C_2H_5OH\). It has two carbon atoms, just like ethane, but one of the hydrogen atoms is replaced by an OH (hydroxyl) group. The chemical structure can be represented as CH3-CH2OH or \(H_3C-CH_2OH\).

Identify the common features of ethane and ethanol

Both ethane and ethanol have two carbon atoms bonded to each other with a single bond, and both have a total of six hydrogen atoms. They are both derivatives of the same parent hydrocarbon, ethylene (C2H4), and are both part of the same homologous series called alkanes - except ethanol is actually an alcohol because of the presence of the hydroxyl group.

Describe the chemical structure of 1-propanol

1-Propanol (also called propan-1-ol) is an organic compound with the molecular formula \(C_3H_7OH\). It has three carbon atoms, one of which is bonded to an OH (hydroxyl) group. The chemical structure can be represented as CH3-CH2-CH2OH or \(H_3C-CH_2-CH_2OH\). It is an alcohol, because it has the hydroxyl group attached to one of the carbon atoms.

Describe the chemical structure of propane

Propane is an organic compound with the molecular formula \(C_3H_8\). It consists of three carbon atoms bonded with single bonds and each carbon atom is connected to the appropriate number of hydrogen atoms. The chemical structure can be represented as CH3-CH2-CH3 or \(H_3C-CH_2-CH_3\). Propane is an alkane, because it only contains carbon-carbon and carbon-hydrogen single bonds.

Compare 1-propanol to propane

The major difference between 1-propanol and propane lies in the presence of the hydroxyl group in 1-propanol. The chemical structure of 1-propanol is CH3-CH2-CH2OH, while that of propane is CH3-CH2-CH3. This difference in functional group makes 1-propanol an alcohol, whereas propane is an alkane. As a result, their physical and chemical properties also differ, such as boiling points, polarity, and reactivity with other substances.

Key concepts

Chemical Structure

Chemical structure is fundamental in organic chemistry as it offers a visual representation of how atoms are arranged in a compound. Understanding these arrangements helps in predicting the behavior and properties of molecules.

• Visual Representation: Chemical structures provide a way to sketch or depict molecules using lines to represent chemical bonds between atoms.
• Formula Illustrations: As seen with ethane (\(C_2H_6\)) and ethanol (\(C_2H_5OH\)), the chemical structure formula shows the exact composition and layout of a molecule.
• Bonds and Atoms: The structures show carbon atoms mainly bonded together with single bonds, and sometimes include one or more functional groups such as hydroxyl groups.

Learning to read and understand these structures allows chemists to elucidate the properties and reactivity of different organic compounds, such as the difference between alkanes and alcohols.

Hydroxyl Group

The hydroxyl group, often symbolized as -OH, is a vital functional group in organic chemistry. It transforms a simple hydrocarbon into an alcohol, changing its properties significantly.

• Basic Definition: A hydroxyl group consists of one oxygen atom bonded to one hydrogen atom. In chemical structures, this group is typically attached to a carbon atom.
• Effect on Molecules: The presence of a hydroxyl group makes the molecule it attaches to an alcohol, which affects its physical and chemical characteristics.
• Reactivity and Polarity: Hydroxyl groups increase the polarity of a molecule, which can elevate its boiling point and its ability to form hydrogen bonds with other molecules.

For example, in the step-by-step exercise, the difference between \(C_2H_6\) and \(C_2H_5OH\) lies precisely in the inclusion of the hydroxyl group in ethanol, converting it from an alkane to an alcohol.

Alkanes

Alkanes are a class of saturated hydrocarbons characterized by having only single bonds between carbon atoms. They are often referred to as paraffins in the context of organic chemistry.

• General Formula: Alkanes generally have the formula \(C_nH_{2n+2}\), where \(n\) is the number of carbon atoms.
• Properties: These compounds are typically nonpolar, due to the absence of any functional groups besides hydrogen and carbon.
• Example: Ethane (\(C_2H_6\)) and propane (\(C_3H_8\)) are simple examples. They consist entirely of carbon-hydrogen bonds with carbon atoms connected by single bonds.

Their stable structure contributes to their relative lack of reactivity compared to other organic compounds, such as alcohols or alkenes, which have double bonds or other functional groups.

Alcohols

Alcohols are organic compounds that possess one or more hydroxyl (-OH) groups attached to a saturated carbon atom. This group is critical for defining their distinct properties.

• Basic Structure: Alcohols replace one or more hydrogen atoms in an alkane with a hydroxyl group, with a general formula of \(R-OH\), where \(R\) is an alkyl group.
• Varied Properties: As seen with ethanol and 1-propanol, the hydroxyl group affects both physical and chemical properties, making alcohols generally more polar with higher boiling points compared to their corresponding alkanes.
• Chemical Behavior: Alcohols are more reactive than alkanes due to the presence of the hydroxyl group, allowing them to engage in hydrogen bonding and increase their solubility in water.

In practical life, alcohols like ethanol are incredibly significant, being utilized in fields ranging from pharmaceuticals to fuels, owing much of their utility to the versatile hydroxyl group.