Orgo 9.1-9.7

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Orgo 9.1-9.7
2013-11-25 23:17:38
CHM 201

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  1. __ are hydrocarbons that contain carbon-carbon triple bonds. They are also called __ because they are derivatives of __, the simplest __.
    • alkynes x3
    • acetylenes
    • acetylene
    • alkyne
  2. The chemistry of the carbon- carbon triple bond is what? A triple bond gives an alkyne what?

    What is it's molecular formula? 

    How many elements of unsaturation (eu) does it have?
    • similar to that of the double bond
    • four fewer hydrogens than the corresponding alkane
    • CnH2n-2
    • two
  3. Naming alkynes:
    - When additional functional grops are present, the suffixes are combined to produce the compound names of the __, __ and so on. 
    - The IUPAC rules gives __ a higher priorty than __ or __, so the numbering begins at what?
    - What happens if the double bond and triple bond are equidistant from the ends of hte chain?
    • alkenynes (a double bond and a triple bond)
    • alkynols (a triple bond and an alcohol)
    • alcohols
    • alkenes
    • alkynes
    • at the end closer to an alcohol
    • number the chain so the double bond receives a lower number than the triple bond
  4. The common names of alkynes describe them as what?

    Most alkynes can be named as a molecule of __ with one or two __.
    • derivatives of acetylene
    • acetylene
    • alkyl substituents
  5. Many of an alkyne's chemical properties depend on whether there is an __, that is, whether the __ comes at the end of a carbon chain. Such an alkyne is called a __ or a __. If the triple bond is located somewhere other than the end of the carbon chain, the alkyne is called an __ or an __.
    • acetylenic hydrogen (H-C***C)
    • triple bond
    • terminal alkyne 
    • terminal acetylene
    • internal alkyne
    • internal acetylene
  6. Alkynes are relatively __ and nearly __ in water. They are quite __ in most organic solvents. Many alkynes have characteristic, mildly offensive __. Ethyne, propyne, and butynes are __ at room temp just liek the corresponding alkanes and alkenes. IN fact, the __ of alkynes are nearly the same as those of alkanes and alkenes with similar C skeletons
    • nonpolar
    • insoluble
    • soluble
    • odors
    • gases
    • BP
  7. __ is a colorless, foul-smelling gas that burns in air with a yellow, sooty flame. WHen the flame is supplied with pure oxygen, the color turns to __, and the flame temp increases dramatically.
    • acetylene
    • blue
  8. Each carbon atom is bonded to two other atoms, and there are no __. Each carbon atoms needs __ to form the __. Hybridization of the __ wwith one __ gives two hybrid orbitals, directed __ degrees apart, for each carbon atom. Overlap of these __ with each other and with the __ gives the __ framework.
    • nonbonding valence electrons
    • two hybrid orbitals
    • sigma bond framework
    • s orbital
    • p orbital 
    • 180
    • sp hybrid orbitals
    • hydrogen s orbitals
    • sigma bond
  9. Two __ result from overlap of the two remaining unhybridized __ on each carbon atom. These orbitals overlap at __ to each other, forming one __ with __ above and below the C-C sigma bond, and the other with __ in front and in back of the sigma bond. The shape of these __ is such that they blend to form a __ of __ encircling the sigma bond between the two carbon atoms
    • pi bonds
    • p orbitals
    • right angles
    • pi bond
    • electron density
    • electron density
    • pi bonds
    • cylinder of electron density
  10. Triple bonds are (shorter/ longer) than double and single bonds.

    The triple bond is relatively __ because of the attractive overlap of __ and the high __ of the sp hybrid orbital. The sp hybrid orbitals are about 1/2 __, using more of the clsoer, hightly held s orbital. The sp hybrid orbitals also account for the slightly __ C-H bonds in acetylene compared with ethylene.
    • shorter
    • shorter
    • three bonding pairs of electrons 
    • s character
    • s character
    • shorter
  11. __ are much more acidic than other hydrocarbons. Removal of an __ proton forms an __, which plays a central role in alkyne chemistry. 

    The acidity of an __ stems from the nature of the __.

    What is the trend of acidity?
    • terminal alkynes
    • acetylenic proton
    • acetylide ion
    • acetylenic hydrogen
    • sp hybrid triple bond C-H bond
    • increases with increasing s character of the orbitals: xp3<sp2<sp
  12. True or False:

    The vinyl proton is about 10^19 times more acidic than the acetylenic proton.
    • False
    • The acetylenic proton is about 10^19 times more acidic than the vinyl proton
  13. Abstraction of an __ gives a __ that has the lone pair of electrons in the sp hybrid orbital. ELectrons in this orbital are __, and there is less __ than in __ with the lone pair in sp2 or sp3 hybrid orbitals.
    • acetylenic proton
    • carbanion
    • close to the nucleus
    • charge separation
    • carbanions
  14. Very strong bases deprotonate __ to form __ called __ Hydroxide ioin and alkoxide ions are not strong enough bases to __. __ do not have __, so they do not react
    • terminal acetylenes
    • carbanions
    • caetylide ions (alkynide ions)
    • deprotonate alkynes
    • internal alkynes
    • acetylenic protons
  15. __ is frequently used as the base in forming __. The __ is the conjugate base of ammonia, a compound that is itself a base. __ is also a very weak acid, however, with a pKa=35. One of its hydrogens can be reduced by __ to ogive the sodium salt of the __, a very strong conjugate base.
    • sodium amide
    • acetylide salts
    • amide ion
    • ammonia
    • sodium metal
    • amide ion
  16. __ are strong nucleophiles. Inf act, one of the best methods for synthesizing substituted alkynes is a __ by an __ on an unhindered alkyl halide.
    • acetylide ions
    • nucleophilic atack
    • acetylide ion
  17. What is the first of the two approaches for synthesis of alkynes?
    1) an appropriate electrophile undergoes nucleophilc attack by an acetylide ion; the electron may be an unhibdered primary alkyl halide (Sn2) or it can be a carbonyl compound (addition to form an --OH), either of which joins two fragments to give a product with a lengthened carbon skeleton
  18. What is the second of the two approaches for synthesis of alkynes?
    2) forms a triple bond by a double dehydrohalogenation of a dihalide; does not enlarge the carbon skeleton; isomerization of the triple bond may occur
  19. An acetylide ion is a __ and a __. What can it do?
    • strong base
    • powerful nucleophile
    • displace a halide ion from a suitable substrate, giving a substituted acetylene
  20. If this Sn2 reaction is to produce a good yield, the alkyl halide must be an __. .It must be __ or __, with no __ or __ close to the reaction center.
    • excellent Sn2 substrate
    • methyl or primary
    • bulky substituents
    • branches
  21. If the back-side approach is hindered, what happens?
    the acetylide ion may abstarct a proton, giving elimination by the E2 mechanism
  22. Like other carbanions, acetylide ions are strong __ and strong __. In addition to displacing halide ions in __, they can add to __. Because oxygen is more electronegative than carbon, the __ is __.
    • nucleophiles
    • bases
    • Sn2 reactions
    • carbonyl groups
    • C=O 
    • polarized
  23. The positively charged carbon is __; attack by a __ places a negative charge on the electronegative oxygen atom. 

    The product of this __ attack is an __, a strong base. (An __ is the conjugate base of an alcohol, a weak acid.) Addition of water or a dilute acid protonates the __ to give the alcohol.
    • electrophilic
    • nucleophile
    • nucleophilic
    • alkoxide ion x3
  24. An __ can serve as the nucleophile in this addition to a __. The __ adds to the __ to form the __. Addition of dilute acid in a separate step protonates the __ to give the __
    • acetylide ion
    • carbonyl group
    • acetylide ion
    • carbonyl group
    • alkoxide ion
    • alkoxide ion
    • alcohol
  25. An __ adds to formaldehyde to give (after the protonation step) a __ with one more carbon atom than there was in the __. 

    An __ adds to an aldehyde to give, after protonation, a __. The two groups of the __ are the __ and the __ that was bonded to the carbonyl group of the aldehyde.
    • acetylide
    • primary alcohol
    • acetylide

    • acetylide
    • secondary alcohol x2
    • acetylide
    • alkyl group
  26. A __ has two alkyl groups bonded to its carbonyl carbon atom. Addition of an __, followed by protonation, gives a __. The three groups bonded to the __ (the carbon bearing the OH group) are the __ and the two __ originally bonded to the carbonyl group in the ketone.`
    • ketone
    • acetylide
    • tertiary alcohol 
    • carbinol carbon atom
    • acetylide
    • alkyl groups