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Organic Chemistry > Alkynes > Flashcards

Alkynes Flashcards

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1
Q

Alkynes has the prefix _______

A

yne

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2
Q

Terminal alkynes

A

Monosubstituted acetylenes

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3
Q

Internal Alkynes

A

Dissubstituted acetlyenes

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4
Q

What are the bases used to protonate an acetylene or terminal alkynes?

A
  1. CH9-
  2. H2N
  3. H-
  4. Acetylide ion
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5
Q

When preparing alkynes they can be formed from dihalides via ___________

A

Strong base

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6
Q

Alkyl dihalides can be turn into alkynes via _______ twice

A

E2 reactioon

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7
Q

Geminal dihalide

A

Both halogens are connected to the same carbon

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8
Q

Vicinal dihalides

A

Two halogens are connected to adjacent carbons

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9
Q

_________ & __________ are the bases used for turning alkyl dihalides into alkynes

A

NaNH2, NH3

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10
Q

A terminal alkyne can be prepared with ___________ soidum amide

A

Excess (xx)

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11
Q

Sodium amide

A

NaNH2

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12
Q

Alkynes can undergo catalytic hydrogenation & also can use a poisoned catalyst to covert alkyne into a _______ alkyne

A

Cis Alkyne

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13
Q

What are the types of poisoned catalyst that can be used to form a cis alkene?

A

Lindlar’s Catalyst

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14
Q

What is the sterochemistry of catalylic hydrogenation involving alkynes?

A

Syn Addition

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15
Q

______________ reduction can turn alkynes into trans alkenes

A

Dissolving metal reduction

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16
Q

What is the reagents used in a dissolving metal reduction?

A

Na in NH3

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17
Q

What is the mechanism for dissolving metal reduction?

A
  1. Nucleophilic attack
  2. Proton transfer
  3. Nucleophilic attack
  4. Proton transfer
18
Q

A ____________ arrow shows the movement of one electron

A

Half arrow (Fish hook arrow)

19
Q

To produce an alkane an alkyne can be treated with _____ & a metal catalyst like Pt,Pd, or Ni

A

H2

20
Q

To produce a Cis alkene an alkyne can be treated with H2 & a _________ catalyst

A

Poisoned Catalyst (like Lindlar’s Catalyst or Ni2B)

21
Q

To produce a trans alkene an alkyne can be treated with ______ in _______

A

Na in NH3

22
Q

Alkynes can undergo hydroboration oxidation, what is the regiochemistry & stereochemistry?

A
  1. Regiochemistry is anti-markonvikov addition
  2. Stereochemistry is syn addition
23
Q

What is the mechanism for hydrohaolgenation with alkynes?

A
  1. Proton transfer
  2. Nucleophilic attack
24
Q

When terminal alkyne is treated with ____________ during hydrohalogenation an anti-Markovnikov addition is obsverved where the Br is positioned at the terminal position which produces E & Z isomers

A

HBr, ROOR (Radical addition can only happen with HBr (Not HCl or HI))

25
Q

Alkyne can undergo acid catalyzed hydration but _________ is used to catalyzed the reaction

A

HgSO4

26
Q

What is the mechanism for Acid - catalyzed hydration tautomerization ?

A
  1. Proton Transfer
  2. Proton Transfer

An resonance - stablized intermediate forms to then form a ketone

27
Q

Tautomers

A

Constitutional isomers that are rapidly intercovertted via the migration of a proton

28
Q

Ketoenol tautomerization

A

Intercoversion between an enol & ketone

29
Q

Alkynes can also undergo hydroboration - oxidation by using ____________ reagents

A

The same reagents

30
Q

What is the mechanism for Base catalyzed tautomerization (hydroboration - oxidation)?

A
  1. Proton transfer
  2. Proton transfer

An enolate ion is formed to then form an aldehyde

31
Q

__________ are used to prevent the 2nd addition of BH3 in an hydroboration - oxidation reaction

A

Dialky boranes (R2BH)

32
Q

What are the two most common dialkyl boranes?

A
  1. Disamyl borane
  2. 9-BBN
33
Q

Having dialkyl boranes as the reagent can turn a terminal alkyne into an ___________

A

Aldehyde

34
Q

Acid - catalyzed hydration of a terminal alkyne produces a ___________ as a product & hydroboration - oxidation produces __________ as the product

A

Methyl Ketone, An Aldehyde

35
Q

Alkynes can udergo halogenation but since it has 2 double bonds (π bonds) it can have ___________

A

4 Halogens (tetrahalide)

36
Q

Can add only 2 halogens to produce a dihalide via _________ where the E isomer is the major product

A

Anti-addition

37
Q

Alkynes can undergo ozonolysis reaction where when treated with O3 & Water it can form __________ as it products

A

Carboxylic Acids

38
Q

When a terminal alkyne undergo oxidative cleavage the terminal side is converted into __________

A

Carbon dioxide ( & carboxylic acid) as products

39
Q

Alkylation

A

Installs an alkyl group onto a terminal alkyne

40
Q

What are the reagents used in alkylation of terminal alkynes ?

A
  1. NaNH2
  2. RX (only methyl or primary alkyl halides)
41
Q

Alkenes can be converted into alkynes via ___________ followed by elimination

A

Bromination

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