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32 Cards in this Set
- Front
- Back
What are carbonyls?
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A structure containing a carbon-oxygen double bond |
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What is special about the bond in carbonyls and why?
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It is polar due to the difference in electro negativities of the Carbon and Oxygen. |
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How to make an aldehyde from an alcohol
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The orange Cr2O7- is reduced to green Cr3+ |
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Show the oxidation reaction of ethanol to ethanoic acid
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CH3CH2OH (l) +[O] -> CH3CHO (l) + H2O (l) |
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Show the oxidation reaction of the secondary alcohol propan-2-ol
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Heated under reflux with acidified potassium dichromate |
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Which is easier to oxidise out of aldehydes and ketones?
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Aldehydes |
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How do you oxidise ketones?
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Use a powerful oxidising agent under vigorous conditions to carboxylic acids but with fewer carbons
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What happens if aldehydes and ketones are heated with a mild oxidising agent?
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Ketone -> no change |
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How to identify a carbonyl compound
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Strong peak at 1400-1600 cm-1 in the infrared spectrum |
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How to determine if ketone or aldehyde after 2,4-DNPH?
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The silver(I) ion is reduced to silver: Ag+(aq) +e- -> Ag (s) Positive result for an aldehyde will form a SILVER MIRROR |
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What type of mechanism occurs with both carbonyls?
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Nucleophilic addition - addition to the polar C=O bond, attack is by nucleophiles at the positive carbon centre. |
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State the reagent, conditions, mechanism and nucleophile for the reduction of carbonyls
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Conditions: aqueous or alcoholic solution Mechanism: Nucleophilic addition Nucleophile: H- (Hydride Ion) |
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What are aldehydes and ketones REDUCED to? |
Ketones: Secondary Alcohols |
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Show reduction equation of ethanal |
CH3CHO + 2[H] -> CH3CH2OH (NO WATER) |
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Show the reduction equation of propan-2-one
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Draw the mechanism for nucleophilic addition of ethanal
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State the conditions, nucleophile and product when a carbonyl is reduced by potassium cyanide
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Heat under reflux Nucleophile: Cyanide ion CN- Product: Hydroxynitrile |
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Explain what Kekule's model of benzene was
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With three localised double bonds |
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What was wrong with Kekule's model? (3 problems)
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Benzene doesn't readily undergo electrophilic addition so doesn't have proper C=C bonds. All bond lengths were similar, when really double bonds are shorter than single ones. The ring was thermodynamically more stable than expected. |
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Explain the now accepted theory of the structure of Benzene.
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The six pi electrons making up the double bonds are delocalised around the ring due to sideways overlapping of the p orbitals. Still gave a PLANAR structure. More stable, didn't undergo electrophilic addition |
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State the reagents, conditions, type of mechanism and product of nitration of benzene?
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Conditions: Catalyst-conc sulphuric acid, reflux at 55 Celsius Mechanism: ELECTROPHILIC SUBSTITUTION Product: Nitrobenzene |
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Show the equation for mononitration of benzene
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C6H6 + HNO3 -> C6H5NO2 +H2O
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Draw and explain the mechanism for the nitration of benzene
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(Google mechanism) An electron pair leaves the delocalised system to form a bond to the electrophile This disrupts the stable delocalised system and forms an unstable carbon cation intermediate To restore stability, the pair of electrons in the CH bond moves back to the ring Overall there is a substitution of hydrogen The electrophile is (NO2)+ |
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Show how the electrophile for the nitrification of benzene is formed
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2H2SO4 + HNO3 (reversible arrow) (2HSO4)- + (H3O)+ + (NO2)+
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Why does the temperature need to be controlled in the nitrification of benzene?
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The higher temp means there is more chance for more nitronium ions to be substituted on to the benzene.
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State the reagents and conditions for the halogenation of benzene
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Reagents: Chlorine Conditions: Reflux in the presence of a halogen carrier such as Aluminium Chloride |
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State the overall equation for the halogenation of benzene |
C6H6 +Cl2 -> C6H5Cl +HCl
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What is the role of the halogen carrier in halogenation of benzene?
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Chlorine is non polar so not a good electrophile. The halogen carrier polarises the halogen. |
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Show the formation of the electrophile for halogenation of benzene
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Cl2 + AlCl3 (reversible arrow) (AlCl4)- + Cl+ Anhydrous aluminium chloride is the catalyst |
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Show the reformation of the halogen carrier
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H+ + (AlCL4)- -> AlCl3 +HCL |
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Compare the electrophilic addition of benzene with alkenes |
The conditions are much tougher than with alkenes because the delocalised system makes benzene more stable and less reactive
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