Arielle Cruz
Alcohols and carboxylic acids are organic compounds that bear some resemblance to each other and can be easily converted from one to another through oxidation or reduction reactions. However, there are ways to distinguish between the two. One method is to consider their reactivity with other compounds. Carboxylic acids, being highly reactive acids, readily donate protons. Alcohols, on the other hand, are only mildly acidic and less reactive. Another distinguishing test is the sodium bicarbonate test, where the evolution of carbon dioxide gas with carboxylic acid indicates its presence. Additionally, in terms of nomenclature, alcohols have the suffix -ol, while carboxylic acids have the suffix -oic acid.
| Characteristics | Alcohols | Carboxylic acids |
|---|---|---|
| Reaction with carbonates and hydrogen carbonates | No reaction | Produces CO2 gas that turns lime water milky |
| Sodium bicarbonate test | No reaction | React to form sodium acetate and carbon dioxide |
| Litmus test | No reaction | Turns blue litmus red |
| Ester test | N/A | Gives off a sweet smell |
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What You'll Learn
- Carboxylic acid reacts with carbonate and hydrogen carbonate to produce CO2 gas, turning lime water milky
- Alcohols do not react with carbonates and hydrogen carbonates
- Carboxylic acid turns blue litmus paper red
- Alcohols do not respond to the litmus test, except phenol
- Carboxylic acids give off a sweet smell when esterified
Carboxylic acid reacts with carbonate and hydrogen carbonate to produce CO2 gas, turning lime water milky
Carboxylic acids can be distinguished from alcohols through their reaction with carbonates and hydrogen carbonates. Carboxylic acids react with carbonate and hydrogen carbonate to produce CO2 gas, which turns limewater milky. This is due to the formation of solid calcium carbonate particles, which appear as a white precipitate in the solution, giving it a milky appearance. This reaction can be used as a test to detect the presence of carbon dioxide gas.
Limewater, a calcium hydroxide solution, is often used in experiments to detect gases because it reacts with carbon dioxide to produce calcium carbonate, a chalk-like solid that makes the solution appear milky. This reaction can be observed when bubbling carbon dioxide gas through limewater, turning it milky and indicating the presence of carbon dioxide.
The chemical equation for this reaction is:
CO2 + Ca(OH)2 --> CaCO3 + H2O
In this equation, carbon dioxide (CO2) reacts with calcium hydroxide (Ca(OH)2) to form calcium carbonate (CaCO3) and water (H2O). The calcium carbonate precipitates as solid particles, creating the milky appearance.
The sodium bicarbonate test, also known as the sodium hydrogen-carbonate test, is another method to distinguish carboxylic acids from alcohols. In this test, carboxylic acid reacts with sodium bicarbonate to form sodium acetate and carbon dioxide gas, which is indicated by brisk effervescence. Alcohols, on the other hand, do not react with carbonates and hydrogen carbonates.
Additionally, carboxylic acids can be identified through a litmus test, as they turn blue litmus paper red, similar to other acids. Alcohols, with the exception of phenol, do not respond to this test.
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Alcohols do not react with carbonates and hydrogen carbonates
One way to distinguish between an alcohol and a carboxylic acid is to observe their reactions with carbonates and hydrogen carbonates. Carboxylic acids react with carbonates and hydrogen carbonates to produce carbon dioxide gas, which turns lime water milky. On the other hand, alcohols do not react with carbonates and hydrogen carbonates.
The reactivity of the compounds is a key differentiator between alcohols and carboxylic acids. Carboxylic acids are highly reactive and have a strong tendency to donate protons. In contrast, alcohols are only mildly acidic and less reactive, although they still possess some tendency to donate protons. This difference in reactivity is the reason why carboxylic acids react with carbonates and hydrogen carbonates, while alcohols do not.
The sodium bicarbonate test, also known as the sodium hydrogen-carbonate test, is often used to experimentally distinguish between alcohols and carboxylic acids. In this test, an aqueous solution of sodium bicarbonate (NaHCO3) reacts with carboxylic acid to produce brisk effervescence due to the evolution of carbon dioxide gas. This reaction can be represented by the equation:
\RCOOH+NaHC{{O}_{3}}\to RCOONa+{{H}_{2}}O+C{{O}_{2}}\uparrow \>
During the test, the evolution of carbon dioxide gas is indicated by the brisk effervescence, which confirms the presence of carboxylic acid. On the other hand, alcohols do not produce this effervescence and, therefore, do not react with sodium bicarbonate.
Another test that can help distinguish between alcohols and carboxylic acids is the iodoform test. The iodoform test involves the reaction of a substance with iodine (I2) and sodium hydroxide (NaOH) to form iodoform (CHI3). Carboxylic acids that have at least three carbon atoms can undergo the iodoform test, producing a yellow precipitate of iodoform. However, alcohols do not produce this yellow precipitate, which helps differentiate them from carboxylic acids.
While not a direct test for carbonates or hydrogen carbonates, the litmus test can also help distinguish between alcohols and carboxylic acids. Carboxylic acids, like any other acid, turn blue litmus paper red. Alcohols, on the other hand, do not respond to this test, except for phenol, which can turn blue litmus paper red.
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Carboxylic acid turns blue litmus paper red
Carboxylic acid is a type of organic acid that contains the carboxyl functional group, denoted by the symbol COOH. It is highly reactive and has a high tendency to donate a proton. When a solution containing carboxylic acid comes into contact with blue litmus paper, the paper turns red. This colour change is due to the acidic nature of the solution, which has a pH level lower than 7. Litmus paper is used to indicate whether a solution is acidic, basic, or neutral. Blue litmus paper is specifically used to test for acidity, turning red when exposed to acids. This is because acids have a pH level lower than 7, while bases have a pH level higher than 7. Red litmus paper, on the other hand, is used to test for basicity, turning blue when exposed to bases.
To distinguish between an alcohol and a carboxylic acid, one can experimentally use the sodium bicarbonate test, also known as the sodium hydrogen-carbonate test. In this test, the compound in question is reacted with sodium bicarbonate. If the compound is a carboxylic acid, it will react to form sodium acetate and carbon dioxide, resulting in a brisk effervescence of carbon dioxide. Alcohols, on the other hand, do not react with sodium bicarbonate. Another method to distinguish between the two is through their reaction with carbonates and hydrogen carbonates. Acid reacts with these compounds to produce carbon dioxide gas, turning limewater milky. Alcohols, however, do not react with carbonates or hydrogen carbonates.
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Alcohols do not respond to the litmus test, except phenol
Alcohols are mildly acidic and possess the tendency to donate protons, but they are not as reactive as carboxylic acids. Alcohols do not respond to the litmus test, which distinguishes between acids and bases, because they are almost neutral. However, phenol, a type of alcohol, is an exception. Phenol is more acidic than other alcohols, and it turns blue litmus paper red. This colour change distinguishes phenol from other alcohols, such as ethanol, which do not change the litmus paper.
The sodium bicarbonate test is another method to distinguish between alcohols and carboxylic acids. Carboxylic acids react with sodium bicarbonate to form sodium acetate and carbon dioxide gas, which causes a brisk effervescence. Alcohols, including phenol, do not react with sodium bicarbonate. This test is considered the best method to distinguish between alcohols and carboxylic acids.
The iodoform test and the reaction with alkali metal are additional methods that can be used to differentiate between alcohols and carboxylic acids. Carboxylic acids can also be identified through a litmus test, as they turn blue litmus paper red, and by an ester test, as they give off a sweet smell upon esterification.
In summary, while alcohols generally do not respond to the litmus test, phenol, a specific type of alcohol, turns blue litmus paper red. This unique behaviour of phenol distinguishes it from other alcohols, such as ethanol, which do not exhibit this colour change.
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Carboxylic acids give off a sweet smell when esterified
Carboxylic acids and alcohols are two distinct classes of organic compounds with different chemical properties. One of the ways to distinguish between the two is by their reaction with sodium bicarbonate (also known as the sodium hydrogen-carbonate test). In this test, the effervescence of carbon dioxide gas indicates the presence of a carboxylic acid. Alcohols, on the other hand, do not react with sodium bicarbonate.
Carboxylic acids and alcohols can also be differentiated by their reaction with carbonates and hydrogen carbonates. Acids react with these compounds to produce carbon dioxide gas, which turns lime water milky. Alcohols, in contrast, do not react with carbonates or hydrogen carbonates.
Another distinguishing test between the two compounds is the litmus test. Carboxylic acids, like any other acid, turn blue litmus paper red. Alcohols, with the exception of phenol, do not respond to this test.
Carboxylic acids can also be distinguished from alcohols by their sweet smell when esterified. Esters are compounds formed by the reaction of a carboxylic acid with an alcohol. This esterification process is a reversible chemical reaction that involves treating a carboxylic acid with an alcohol in the presence of a dehydrating agent, such as sulfuric acid. The resulting esters often have a pleasant, fruity odor, which is why they are commonly used in fragrances and flavors. The sweet smell of esters is due to the absence of hydrogen bonds between their molecules, resulting in lower vapor pressure than their parent carboxylic acids and alcohols.
The sweet smell of esterified carboxylic acids is not limited to synthetic fragrances and flavors. Esters are also found naturally in many fruits, giving them their characteristic odors. For example, the odor of ripe bananas is due to the presence of esters. Additionally, carboxylic acids, such as acetic acid in vinegar, contribute to the distinct smells of various food products.
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Frequently asked questions
Carboxylic acid is very reactive and has a high tendency to donate a proton. Alcohols, on the other hand, are only mildly acidic and are not as reactive.
In this test, an aqueous solution of sodium bicarbonate (NaHCO3) will produce brisk effervescence due to the evolution of CO2 gas when reacting with a carboxylic acid. Alcohols do not react with sodium bicarbonate.
Carboxylic acid turns blue litmus paper red. Alcohols do not respond to this test except for phenol.
Acid reacts with carbonate and hydrogen carbonate to evolve CO2 gas that turns lime water milky. Alcohols do not react with carbonates and hydrogen carbonates.
