Orgo 10.10-10.12

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  1. __ and __ are strong nucleophiles and strong bases. Besides tehir additions to carbonyl compounds, they react with other acidic or electrophilic compounds. In some cases, these are useful reactions, but they are often seen as annoying side reactions where a small impurity of water or an alcohol destroys the reagent.
    • GR
    • organolithium reagnets
  2. __ and __ react vigorously and irreversibly with water. Therefore, all reagents and solvents used in these reactions must be __.
    • GR
    • organolithium reagents
  3. Why would we ever want to add an organometallic reagent to water?

    The overall reaction is a __because it replaces the __ with a __. In particular, this reaction is a way to label a compound with __at any position where a halogen is present
    This is a method for reducing an alkyl halide to an alkane.

    • reduction 
    • electronegative halogen atom
    • hydrogen atom
    • deuterium
  4. In addition to O-H groups, the protons of __ and __ groups and the hydrogen atom of a terminal alkyne, __, are sufficiently acidic to protonate __ and __. Unless we want to protonate the reagent, compounds with these groups are considered incompatible with __ and __.
    • N-H
    • S-H
    • -C***C-H
    • Grignard and organolithium reagents x2
  5. Why are GRs useful?

    However, we must make sure that the only electrophilic double bond in the solution is the __.
    There must be no __ in the solvent or in the __ itself, or they will be attacked as well.

    Any multiple bond involving a strongly electronegative element is likely to be atacked, including __(5)__.
    because they add to the electrophilic double bonds of carbonyl groups.

    • one we want the reagent to attack
    • eectrophilic double (or triple) bonds 
    • GR 

    • C=O
    • S=O
    • C=N
    • N=O
    • C***N
  6. Grignard reagents convert carbonyl compounds to alcohols by __. __ add a hydride ion, reducing the carbonyl group to an alkoxide ion with no additional carbon atoms. Subsequent __ gives the __. Converting a __ or an __ to an alcohol involves __.
    • adding alkyl groups
    • hydride reagents
    • protonation
    • alcohol
    • ketone
    • aldehyde
    • adding two hydrogen atoms across the C=O bond: a reduction
  7. The two most useful hydride reagents, __ and __, reduce carbonyl groups in excellent yields. These reagents are called __ because they do not have a simple hydride structure. Instead, their hydrogen atoms, bearing __, are covalently bonded to __ and __ atoms. This arrangement makes the hydride a better nucleophile while reducing its __.
    • sodium borohydide
    • lithium aluminum hydride
    • complex hydrides
    • partial negative charges
    • boron
    • aluminum atoms
    • basicity
  8. __ is less EN than __, so more of the negative charge in the AlH4- is borne by the H atoms. Therefore, __ is a much stronger reducing agent, and it is much more difficult to work with than __. __ reacts explosively with water and alcohols, liberating H gas and sometimes starting fires. __ reacts slowly with alcohols and with water as long as teh pH is high (basic). __ is a convenient and highly selective reducing agent.
    • Aluminum
    • boron
    • lithium aluminum hydrinde (LAH)
    • sodium borohydride
    • LAH
    • sodium borohydride x2
  9. Sodium borohydride (NaBH4) reduces __ to __, and __ to __. The reactions take place in a wide variety of solvents with excellent yields.
    • aldehydes
    • primary alcohols
    • ketones
    • secondary alcohols
  10. Sodium borohydride is __; it usually does not react with carbonyl groups that are less reactive than __ and __. For example, __ and __ are unreactive toward borohydride reduction. Thus, sodium borohydride can reduce a __ or an __ in the presence of an __ or an __.
    • selective
    • ketones
    • aldehydes
    • carboxylic acids
    • esters
    • ketone 
    • aldehyde
    • acid 
    • ester
  11. __ is a much stronger reagent than __. It easily reduces __ and __ and also the less-reactive carbonyl groups: those in __, __, and other __. __ reduces __ to secondary alcohols, and it reduces __, __, and __ to primary alcohols. The lithium salt of the alkoxide ion is initially formed, then the (CAUTIOUS!) addition of dilute acid protonates the alkoxide.
    • lithium aluminum hydride
    • sodium borohydride
    • ketones
    • aldehydes
    • acids
    • esters
    • acid derivatives
    • LAH
    • ketones
    • aldehydes
    • acids
    • esters
  12. In summary, sodium borohydride is the best reagent for reduction of a simple __ or __. Using NaBH4, we can do what but not what?
    • ketone
    • aldehyde
    • reduce a ketone or an aldehyde in the presence of an acid or an ester, but we can't reduce an acid or ester in the presence of a ketone or aldehyde
  13. Reducing a ketone or an aldehyde to an alcohol involves what? 

    This addition can be accomplished by __, commonly using __ as the catalyst.
    • adding two hydrogen atoms across the C=O bond
    • catalytic hydrogenation
    • Raney nickel
  14. __ is a finely divided hydrogen-bearing form of nickel made by treating a nickel-aluminum alloy with a strong __ solution. THe aluminum in the alloy reacts to form hydrogen, leaving behind a finely divided nickel powder saturated with hydrogen.
    • Raney nickel
    • sodium hydroxide
  15. __ is an effective catalyst for the __of ketones and aldehydes to alcohols. 

    __ are also reduced under these conditions, however, so any alkene double bonds in the starting material will also be reduced. In most cases, __ is more convenient for reducing simple ketones and aldehydes.
    • Raney nickel
    • hydrogenation
    • Carbon-carbon double bonds
    • sodium borohydride
  16. __ are sulfur analogues of alcohols, with an -SH group in place of the alcohol -OH group. __ are also called __ because they form stable heavy-metal derivatives.
    • Thiols x2
    • mercaptans
  17. Thiols' ability to complex heavy metals has proved useful for making __ to __.
    Although oxygen is more EN than sulfur, __ are more acidic than __. Their enhanced acidity results from two effects: What are they?
    • antidotes
    • heavy-metal poisoning
    • thiols
    • alcohols
    • 1) S-H bonds are generally weaker than O-H bonds, making them easier to break
    • 2) thiolate ion has its negative charge on sulfur, which allows the charge to be delocalized over a larger region than the negative charge of an alkoxide ion, borne on a smaller oxygen atom.
  18. __ are easily formed by treating the __ with aqueous __. 

    Thiols can be prepared by __ of __ with unhindered alkyl halides. The thiol product is still __, so a large excess of __ is used to rpevent the product from undergoing a __ to give a __.
    • Thiolate ions
    • thiol
    • sodium hydroxide
    • Sn2 reactions
    • sodium hydrosulfide
    • nucleophilic
    • hydrosulfide
    • second alkylation 
    • sulfide
  19. Unlike alcohols, __ are easily oxidized to give a dimer called a __. The reverse reaction, __, takes place under reducing conditions.
    • thiols
    • disulfides
    • reduction of the disulfide to thiols
  20. Just as mild oxidation converts thiols to disulfides, vigorous oxidation converts them to __, with __, __ or even __ as the oxidant for this reaction. Any Lewis structure of a __ requires either separation of formal charges or more than eight electrons around sulfur.
    • sulfonic acids
    • KMnO4
    • nitric acid
    • bleach (NaOCl)
    • sulfonic acid
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Orgo 10.10-10.12
2013-12-21 19:24:30
CHM 202
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