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39 Cards in this Set
- Front
- Back
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What are alcohols? What are their general formula?
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These are compounds that have hydroxyl (OH) groups bonded to sp3-hybridised carbon atoms. Their general formula is R-OH
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What is meant by primary, secondary and tertiary alcohols?
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The carbon directly attached to the hydroxyl group in an alcohol can be attached to 1, 2 or 3 carbon atoms (R groups).
Therefore a primary alcohol will have 1 R group (and two hydrogens), a seondary alcohol will have 2 R groups (and one hydrogen) and a tertiary alcohol will have 3 R groups (and no hydrogens) directly attached to the carbon bound to the hydroxyl (OH) group. |
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Name and discuss the 2 types of bonding between alcohols.
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Since alcohols are made of a water-like OH group and a hydrocarbon-like R group, they exhibit properties of both.
Therefore, alcohols create hydrogen bonds between the hydroxyl groups and hydrophobic interactions between the hydrocarbon chains. |
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Discuss the solubility of alcohols in water.
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Alcohols have hydrocarbon and water-like properties. The shorter the alkyl groups in an alcohol, the more the alcohol will behave like water and be more soluble.
The same hold true for the opposite. The longer the hydrocarbon chains, the less soluble the alcohol becomes. |
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Discuss the acidity and basicity of alcohols.
Hint: consider bronsted-lowry vs. lewis definitions |
Bronsted-Lowry acids are proton donors.
Alcohols are very weak Bronsted-Lowry acids and form alkoxides(-) when they deprotonate their hydroxyl group. [note that alcohol acidity decreases as alkyl groups increase in length but acidity is increases by halogens.] Lewis bases are electron pair donors. Alcohols are lewis bases as they can be protonated to form alkyloxonium ions(+). [note that this is the first step in the dehydration of alcohols] |
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List the four major reactions with alcohols.
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Oxidation
Dehydration Esterification Reactions with bases |
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Which reactions with alcohols occur across the C-O bond?
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Oxidation
Dehydration |
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Which reactions with alcohols occur at the O-H bond (in the hydroxyl group)?
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Esterifiaction
Reaction with bases |
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Using words, briefly describe the general process of dehydration of alcohols.
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An alcohol will be heated with a strong acid to eliminate a water group and produce an alkene.
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Explain in detail the mechanism of dehydration of alcohols.
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Begin with an alcohol, a strong acid (H+) and heat.
Since the oxygen in the hydroxyl group has lone pairs of electrons, one pair will form a bond with H+ to form a protonated alcohol intermediate (H2O+). This water substituent is a good leaving group and will leave the rest of the hydrocarbon (C-O bond breaks) to form a positively charged carbocation. The carbocation will then lose a proton (H+) to compensate for the positive charge to form an alkene pi bond according to Zaitzev's rule. |
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Define Zaitzev's Rule
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The more alkyl-substituted alkene is formed preferentially.
[Applied to the dehydration of alcohols] |
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List the four major reactions with alcohols.
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Oxidation
Dehydration Esterification Reactions with bases |
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This reaction of alcohols forms carbonyl compounds.
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Oxidation
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In the oxidation of alcohols there is a gain of ______ and/or a loss of ______.
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In the oxidation of alcohols there is a gain of oxygen and/or a loss of hydrogen.
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Which reactions with alcohols occur across the C-O bond?
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Oxidation
Dehydration |
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Which reactions with alcohols occur at the O-H bond (in the hydroxyl group)?
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Esterifiaction
Reaction with bases |
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What type of alcohol cannot undergo oxidation? Why?
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Tertiary alcohols can't undergo oxidation because they have no hydrogens to substitute.
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Oxidation of a primary alcohol will produce a(n) _______. Further oxidation of this product will yield a(n) _______.
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An oxidised primary alcohol will form an aldehyde.
An oxidised aldehyde will form a carboxylic acid. |
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Using words, briefly describe the general process of dehydration of alcohols.
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An alcohol will be heated with a strong acid to eliminate a water group and produce an alkene.
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Explain in detail the mechanism of dehydration of alcohols.
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Begin with an alcohol, a strong acid (H+) and heat.
Since the oxygen in the hydroxyl group has lone pairs of electrons, one pair will form a bond with H+ to form a protonated alcohol intermediate (H2O+). This water substituent is a good leaving group and will leave the rest of the hydrocarbon (C-O bond breaks) to form a positively charged carbocation. The carbocation will then lose a proton (H+) to compensate for the positive charge to form an alkene pi bond according to Zaitzev's rule. |
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Define Zaitzev's Rule
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The more alkyl-substituted alkene is formed preferentially.
[Applied to the dehydration of alcohols] |
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This reaction of alcohols forms carbonyl compounds.
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Oxidation
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In the oxidation of alcohols there is a gain of ______ and/or a loss of ______.
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In the oxidation of alcohols there is a gain of oxygen and/or a loss of hydrogen.
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What type of alcohol cannot undergo oxidation? Why?
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Tertiary alcohols can't undergo oxidation because they have no hydrogens to substitute.
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Oxidation of a primary alcohol will produce a(n) _______. Further oxidation of this product will yield a(n) _______.
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An oxidised primary alcohol will form an aldehyde.
An oxidised aldehyde will form a carboxylic acid. |
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Oxidation of a secondary alcohol will produce a(n) _____. Further oxidation of this prodcut will produce a(n) _____.
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Oxidation of a secondary alcohol will produce a ketone. Further oxidation of this prodcut is not possiblt because there are no more hydrogens to substitute.
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Name a typical oxidising agent.
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KMnO4
Jones' reagent [chromium trioxide in sulfuric acid] |
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Predict the possible product(s) of the oxidation of ethanol
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Oxidation of ethanol will produce ethanal (aldehyde). Oxidation of ethanal (acetaldehyde) will produce ethanoic (acetic) acid which is a carboxylic acid.
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Predict the possible product(s) of the oxidation of 2-propanol
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Oxidation of 2-propanol will produce propanone (ketone).
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Briefly outline esterification of alcohols. What are the reactants, product(s) and catalyst(s)?
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Esterification:
In the presence of H+, a carboxylic acid and an alcohol will react to form an ester and water. |
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In esterification, how does the carboxylic acid and alcohol combine to form an ester?
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The hydroxyl group of the carboxylic acid is replaced by an alkoxy (OR) group of the alcohol.
An alkoxy group is essentially a deprotonated alcohol. |
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In the formation of water (HOH) in the esterification of alcohols, which reactant loses an OH- group and which reactant loses an H+?
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To form water, the carboxylic acid loses its hydroxyl (OH) and the alcohol is deprotonated to yield an H+ ion.
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This reaction of alcohols forms alkoxide ions. Along what bond in alcohols does this reaction occur?
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Alcohols react with strong bases to form alkoxide ions. The reaction occurs along the O-H bond in alcohols.
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This alcohol is a CNS depressant
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Ethanol
effects resemble the response to anaethetics |
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At what blood-alocohol content would you expect nausea and loss of consciousness?
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Blood ROH of 0.3-0.4%
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Alcohol is predominantly absorbed here.
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The stomach (& some in the small intestine).
Ethanol also stimulates the production of acid. |
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How can alcohol consumption cause dehydration.
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Ethanol inhibits production of a hormone that regulates urine flow (putuitary gland) causing increased urine production.
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How is ethanol processes as a toxin in the body?
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ADH (alcohol dehydrogenase) or Cytochrome P450 with coenzyme NAD convert ethanol into ethanal which is then converted to ethanoic acid.
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True or False:
Ethanol directly causes hangovers. |
False
Ethanol is converted to ethanal which is reponsible for hangovers. |
