Question

Environmentally-Safe Propellants Hydrofluoroalkanes (HFAs) are replacing chlorofluorocarbons in hand-held asthma inhalers, because of CFC damage to the ozone layer. Draw the structures of the HFAs listed below. a. \(1,1,1,2,3,3,3\) -heptafluoropropane b. \(1,1,1,2,\) -tetrafluoroethane

Short answer

The structures of the two hydrofluoroalkanes are as follows: a. 1,1,1,2,3,3,3-heptafluoropropane: F F F | | | F-C-C-H-C-F | | | F F F b. 1,1,1,2-tetrafluoroethane: F F F | | | F-C-C-H | | H H

Step-by-step solution

Identify the hydrocarbon base

In both cases, we have to identify the hydrocarbon base and then replace some hydrogen atoms with fluorine atoms according to the given names. a. In the case of 1,1,1,2,3,3,3-heptafluoropropane, the hydrocarbon base is propane, which has three carbon atoms and eight hydrogen atoms (\(C_3H_8\)). b. For 1,1,1,2-tetrafluoroethane, the hydrocarbon base is ethane, which has two carbon atoms and six hydrogen atoms (\(C_2H_6\)).

Replace hydrogen atoms by fluorine atoms according to the given names

Now we replace the hydrogen atoms with fluorine atoms according to the given names. a. In 1,1,1,2,3,3,3-heptafluoropropane, there are seven fluorine atoms, and the numbers in the name indicate their positions. On the first carbon, there are three fluorine atoms replacing three hydrogen atoms. On the second carbon, there is one fluorine atom replacing one hydrogen atom. Finally, on the third carbon, there are three fluorine atoms replacing three hydrogen atoms. The structure of 1,1,1,2,3,3,3-heptafluoropropane is \(CF_3CHFCF_3\). b. In 1,1,1,2-tetrafluoroethane, the four fluorine atoms replace the hydrogen atoms at the positions indicated by their numbers. The first carbon has three fluorine atoms replacing three hydrogen atoms, while the second carbon has one fluorine atom replacing one hydrogen atom. The structure of 1,1,1,2-tetrafluoroethane is \(CF_3CH_2F\).

Draw the structures of the hydrofluoroalkanes

Finally, we can draw the structures of these two hydrofluoroalkanes: a. The structure of 1,1,1,2,3,3,3-heptafluoropropane: F F F | | | F-C-C-H-C-F | | | F F F b. The structure of 1,1,1,2-tetrafluoroethane: F F F | | | F-C-C-H | | H H

Key concepts

Structure Drawing

When drawing structures of hydrofluoroalkanes (HFAs), it's important to first understand their naming convention. Each name gives clues about the structure of the molecule.
For example, in "1,1,1,2,3,3,3-heptafluoropropane", "hepta" signifies seven fluorine atoms.
The numbers tell us which carbon in the propane base has a fluorine substitution instead of hydrogen.

• Start by identifying your hydrocarbon base: for instance, propane has three carbons.
• Replace the hydrogen atoms with fluorine atoms as specified in the name.
• The numbers indicate the position of substitution. For example, three fluorines on the first carbon "1,1,1" and two on the third carbon "3,3,3".

This approach helps ensure the correct depiction of molecular structures and enhances understanding of how structural variations affect molecular properties.

Ozone Layer

The ozone layer is a vital part of Earth's atmosphere, playing a crucial role in protecting life on our planet.
It is primarily found in the stratosphere and absorbs the majority of the sun's harmful ultraviolet radiation.
In the past, chlorofluorocarbons (CFCs), used in many products, were found to severely damage the ozone layer.

• CFC molecules break apart due to UV radiation, releasing chlorine atoms.
• These chlorine atoms can destroy thousands of ozone molecules per single atom, thinning the layer.

The thinning of the ozone layer results in increased UV exposure, leading to health risks such as skin cancer.
This understanding has driven the search for alternatives that do not deplete the ozone layer.

Chlorofluorocarbons Replacement

Chlorofluorocarbons, once widely used as refrigerants and propellants, have been largely phased out due to their harmful environmental impact.
They were replaced by hydrofluoroalkanes (HFAs), which are less harmful to the ozone layer. HFAs are preferred because they do not contain the chlorine that can destroy ozone molecules.
Instead, they consist of carbon, hydrogen, and fluorine. Although HFAs are not perfect, as they can contribute to global warming, they are a step in the right direction towards sustainable solutions.

• Earlier replacements often contained fewer chlorine molecules, reducing their ozone-depleting potential.
• Current replacements, like HFAs, further minimize environmental impact by excluding ozone-damaging elements altogether.

This transition underscores the importance of continuous innovation for safeguarding our environment.

Environmentally-Safe Propellants

Environmentally-safe propellants are those that accomplish their intended function without causing significant harm to the environment.
Hydrofluoroalkanes (HFAs) are considered one of the more eco-friendly options available today compared to their predecessors. HFAs are used in various applications, such as in medical inhalers, due to their relatively low environmental impact.

• They do not produce the chlorine free radicals that deplete the ozone layer when released into the atmosphere.
• HFAs are designed to strike a balance between functionality and environmental safety, addressing both health and environmental needs.

Switching to environmentally-friendly propellants like HFAs reflects our commitment to and understanding of ecological preservation while meeting technological and medical advancement needs.