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Questions and Answers
Which reducing agent is more powerful for the reduction of esters and carboxylic acids compared to aldehydes and ketones?
What type of compounds do Grignard reagents belong to?
What is the primary product when primary alcohols are oxidized?
Which reaction type involves the removal of water from an alcohol to form an alkene?
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What happens to tertiary alcohols when exposed to oxidizing agents?
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Which halogen can be used for the formation of Grignard reagents?
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What is the primary outcome of alcohol oxidation?
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During dehydration of alcohols, which groups are eliminated to form an alkene?
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What is the role of nicotinamide adenine dinucleotide (NAD+) in biological oxidation?
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Which product is formed when ethanol is oxidized in the body?
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What type of reaction occurs when an alcohol reacts with a carboxylic acid to form an ester?
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Why is the reaction of alcohol with acyl chloride preferred over carboxylic acids for ester formation?
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What is the main catalyst used in the Fischer esterification reaction?
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In the Williamson ether synthesis, what type of halides works best for the reaction?
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What toxic product is formed from the oxidation of methanol?
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What derivative is formed from an alcohol and phosphoric acid?
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What is the role of converting an alcohol into an alkyl halide?
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Which of the following statements is true regarding the Jone's Test?
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What is the primary advantage of using tosylates and mesylates over direct conversion to alkyl halides?
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In the Lucas test, how do 2° alcohols react compared to 1° alcohols?
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What gas is produced when sodium reacts with alcohols in the sodium metal test?
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What is the classification of an alcohol with one carbon bonded to the hydroxyl-bearing carbon?
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What suffix is used to name alcohols?
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How are alcohols with two hydroxyl groups named?
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Which method is NOT commonly used for the industrial production of ethanol?
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In the reduction of carbonyl compounds, what type of bond does the addition of hydrogen affect?
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Which alcohol is derived from the reduction of a carboxylic acid?
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What is the correct order for naming substituents in alcohol nomenclature?
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What happens during the hydration of alkenes in the context of alcohol synthesis?
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Study Notes
Alcohol Structure and Classification
- An alcohol is an organic compound with one or more hydroxyl groups (-OH groups) bonded to a carbon atom.
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Monohydric alcohols are classified as primary (1°), secondary (2°), and tertiary (3°) alcohols based on the number of carbons bonded to the hydroxyl-bearing carbon.
- 1° Alcohol: One or no carbon bonded to the -OH bearing carbon.
- 2° Alcohol: Two carbons bonded to the -OH bearing carbon.
- 3° Alcohol: Three carbons bonded to the -OH bearing carbon.
Nomenclature of Alcohols
- The longest carbon chain containing the -OH group is named by dropping the final -e from the alkane name and adding the suffix -ol.
- The hydroxyl group takes precedence over double and triple bonds when numbering the carbon chain.
- Diols (or glycols) are alcohols with two -OH groups. The alkane name is retained, and the suffix diol is used.
Synthesis of Alcohols
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Industrial production of ethanol:
- Fermentation of sugars
- Hydration of ethene
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Laboratory-scale synthesis of alcohols:
- Hydration of alkenes: Catalyzed by acid.
- Reduction of carbonyl compounds: Aldehydes, ketones, carboxylic acids, and esters.
- Grignard reagents: Nucleophilic addition to carbonyl compounds.
- Hydrolysis of halogenoalkanes (alkyl halides).
- Hydrolysis of esters.
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Reduction of carbonyl compounds:
- Adds hydrogen to a C=O bond to give an alcohol.
- Aldehydes, ketones, carboxylic acids, and esters can be reduced.
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Reduction of carboxylic acids and esters:
- Requires a stronger reducing agent like lithium aluminum hydride (LiAlH4) due to slower reaction rates.
- Produces primary alcohols.
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Grignard Reagents:
- Formed when alkyl halides (RX) react with magnesium metal in ether solvent.
- Produce alkyl-magnesium halides (RMgX) or Grignard reagents.
- These are organometallic compounds with a carbon-metal bond.
Physical Properties of Alcohols
- Boiling point: Higher than alkanes of similar molecular weight due to hydrogen bonding.
- Solubility: More soluble in water than alkanes due to hydrogen bonding, but decreases as the carbon chain length increases.
Reactions of Alcohols
- Dehydration to alkene: Removal of water from a molecule in the presence of a strong acid.
- Oxidation to aldehyde, ketone, or carboxylic acid: Primary alcohols yield aldehydes or carboxylic acids; secondary alcohols yield ketones. Tertiary alcohols do not typically react with oxidizing agents.
- Reduction to alkane: Addition of hydrogen.
- Esterification: Reaction with a carboxylic acid to produce an ester.
- Tosylation: Reaction with tosyl chloride to form a tosylate ester.
- Williamson synthesis of ether: Formation of the alkoxide ion followed by reaction with an alkyl halide.
- Substitution to form alkyl halide: Reaction with hydrogen halides, phosphorus halides, thionyl chloride, or tosylate to form an alkyl halide.
Conversion of Alcohols to Alkyl Halides
- Importance: Converts a poor leaving group (alcohol) into a good leaving group (alkyl halide), allowing for further functional group transformations.
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Methods:
- Reaction with hydrogen halides (HCl, HBr, HI).
- Reaction with phosphorus halides.
- Reaction with thionyl chloride.
- Reaction with tosylate to form a tosylate ester.
Qualitative Tests for Alcohols
- Sodium metal test: Sodium reacts with alcohols, producing hydrogen gas.
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Jone’s test: Sodium dichromate in acid medium (Na2Cr2O7/H2SO4):
- 1° and 2° alcohols give a positive reaction (orange dichromate ion changes to greenish-blue chromic ion).
- 3° alcohols do not react.
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Lucas test: ZnCl2 in concentrated HCl:
- 1° alcohols react slowly or not at all.
- 2° alcohols react in 1-5 minutes.
- 3° alcohols react in less than 1 minute.
- Iodoform test: Positive for ethanol and 2° alcohols but not 3° alcohols.
Biological Oxidation of Alcohols
- Catalyzed by alcohol dehydrogenase (ADH).
- Oxidizing agent is nicotinamide adenine dinucleotide (NAD+).
- Ethanol oxidizes to acetaldehyde, then acetic acid.
- Methanol oxidizes to formaldehyde, then formic acid, which is more toxic than methanol.
- Ethylene glycol oxidizes to oxalic acid, which is toxic.
- Excess ethanol is used to treat methanol and ethylene glycol poisoning.
Enzymatic Oxidation of Alcohols
- Alcohol dehydrogenase catalyzes the removal of two hydrogen atoms from an alcohol molecule.
- NAD+ acts as the oxidizing agent.
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Description
This quiz covers the structure, classification, and nomenclature of alcohols, detailing their hydroxyl groups and the distinctions between monohydric and dihydric types. Learn about the industrial synthesis of ethanol and the naming conventions in organic chemistry. Test your understanding of these essential concepts.
