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CHEM 264 Organic Chemistry > Chapter 7 Alkenes and Alkynes 1 > Flashcards

Chapter 7 Alkenes and Alkynes 1 Flashcards

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1
Q

What are the simplest alkene and alkyne possible?

A

Simplest alkene: Ethylene

Simplest Alkyne: Acetylene

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2
Q

What is the structure in the image?

A

Ethylene

The simplest alkene

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3
Q

What is the molecule in the image?

A

Propylene OR

1-propene (prop-1-ene)

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4
Q

What is the relationship between the two molecules/

A

Diastereomers

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5
Q

What is the difference between the E and Z stereochemistry?

A
  • E: entegegan = opposite
    • highest substituents are on opposite sides
  • Z: zusammen = Same
    • highest substituents are on the same side
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6
Q

Are the compounds the same?

A

No, they are diastereomers and we can differentiate them by using the E and Z nomenclature

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7
Q

What is the functional group in the image?

A

Vinyl group

eg:

Vinyl chloride

(1-chloroethene)

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8
Q

What is the functional group in the image?

Provide an example of a compound with the functional group

CH3CH=CH−X

A

Allyl group or “Propenyl Group”

Eg

Allyl chloride

(3-chloropropene)

Cl—C—C=C

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9
Q

What is the functional group in the image?

Provide an example of a compound with the functional group

A

Benzyl group

eg: Benzyl bromide

6-member benzene with CH2

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10
Q

What is the functional group in the image?

Provide an example of a compound with the functional group

A

Phenyl group

eg: Phenyl bromide “bromobenzene”

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11
Q

What are the four naming rules for alkynes?

A
  1. Find longest chain w/ max number of multiple bonds
  2. Number from end to give 1st multiply bonded position the lowest number
  3. Drop “ane” and add “yne”
  4. For multiple triple bonds, drop the ne and add diyne, triyne etc
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12
Q

What is the compound in the image?

A

Ethyne

“Acetylene”

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13
Q

What are the names of the three compounds?

Are they related?

A

Propyne

1-butyne

2-butyne

  • 1-butyne and 2-butyne are structural isomers
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14
Q

What is the name of the compound?

A

2,4 - Octadiyne

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15
Q

What is the name of the compound?

A
  • 13 Carbons = trideca
  • triple bond (triyne) on 5, 7, 9
  • 3 double bonds (triene) on 1, 3, 11
  • 3=4 E (opposite)
  • 11=12 E (opposite)

= 3E,11E-trideca-1,3,11-triene-5,7,9-triyne

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16
Q

What is the relative polarity of alkanes, alkenes and alkynes?

A

Alkynes > Alkenes > Alkanes

most polar -> least polar

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17
Q

What is the relative acidity of Alkanes, alkenes and alkynes?

A

Least acidic -> most acidic

Alkane < Alkene < Alkynes

Least polar -> Most polar

18
Q

What three properties are higher in alkynes than in alkenes and alkanes?

A

Alkynes have a higher boiling point, melting point, and density

19
Q

What is Hydrogenation?

A
  • “add’n of hydrogen to an alkene in presence of metal catalysts to produce alkanes”
  • Reaction from the addition of H2
  • Stereospecific
  • cis or syn add’n
  • Metal catalysts
20
Q

How do catalysts increase the rate of reaction?

A

Provide a lower energy pathway.

  • are not permanently converted to other products
21
Q

What are the relative stabilities of alkenes?

(1-butene vs trans-2-butene vs cis-2-butene)

A

Trans is most stable and 1-butene (unsubstituted) is the least stable.

Trans-2-butene > Cis-2-butene > 1-butene

22
Q

The ______ on a double bond, the more stable

A

The more substituents on a double bond, the more stable

23
Q

Why are double bonds with more substituents more stable?

A

Carbons on a double bond have a partially positive charge which is stabilized by the e- donating effects of alkyl groups

hydrogens are less e- donating= less stable

24
Q

Why are cis alkenes less stable than trans alkenes?

A

cis alkenes have methyl groups facing the same direction which causes unfavourable steric interactions = decreases stability

25
Q

what is the compound in the image?

A

Fat:

  • A triglyceride: triester of glycerol
  • polyunsaturated (>1 double bond)
26
Q

What is the reaction converting a polyunsaturated triglyceride into a saturated fat?

A

Hydrogenation of Polyunsaturated triglyceride:

  • polyunsaturated triglyceride –(H2)/Ni–>
  • removes double bonds
  • saturated fat (triglyceride)
27
Q

What is the compound in the picture?

A

Diacetyl

butter flavouring that add yellow colour to margarine

IUPAC = butanedione or butane-2,3-dione

28
Q

Why do deuteriums add to the back of steroids in a hydrogenation rxn?

(deuteriums are isotope of Hydrogen 2H)

A

Because of steric hindrance of the nearby methyl group

29
Q

Products: Two possible diastereomers depending on bottom or top addn

Bottom: equatorial isopropyl and axial methyl

Top: isopropyl and methyl are equatorial

A

Hydrogenation reaction requiring a metal catalyst and H2

30
Q

What is halogenation?

A

Add’n of halogens across a double bond

Converts alkene to alkane

31
Q

Halogenation of cyclopentene produces 1:1 racemate of trans-1,2-dibromocyclopentane enantiomers (RR; SS)

Requires:

A

Halogenation of cyclopentene requires Br2 and achiral solvent and produces:

32
Q

Halogenation of 1,2-dimethylcyclopentene produces trans-1,2-Dibromo-1,2-dimethylcyclopentane

And requires: ____

A

Halogenation of 1,2-dimethylcyclopentene produces ____________

And requires: Br2

33
Q

What is Markovnikov’s Rule?

A

In an addition reaction, the positive end of an A-B system (eg I-Cl) adds to the least substituted end of the double bond to make the more stable carbocation

34
Q

Which is faster, intermolecular or intramolecular reactions?

A

Intramolecular reactions are faster: within the same molecule

Therefore, intramolecular almost always beats intermolecular reactions

35
Q

What is Zaitsev’s rule?

A

Formation of the more substituted alkene is favored with a small base.

  • if we use a small base (eg ethoxide or hydroxide) the major product of the rxn will be the more highly substituted alkene (more stable alkene)
36
Q

Whenever an elimination occurs to give the more stable, more highly substituted alkene, chemists say that the elimination follows _______

A

Whenever an elimination occurs to give the more stable, more highly substituted alkene, chemists say that the elimination follows Zaitsev’s rule

37
Q

What is kinetic control of product formation?

A

The preferential formation of one product b/c the free energy of activation leading to its formation is lower than that for another product, and therefore the rate of its formation faster

38
Q

Carrying out dehydrohalogenations with a bulky base such as potassium tert-butoxide (t-BuOK) in tert-butyl alcohol (t-BuOH) favours the formation of:

A

Carrying out dehydrohalogenations with a bulky base such as potassium tert-butoxide (t-BuOK) in tert-butyl alcohol (t-BuOH) favours the formation of the less substituted alkene

39
Q

When an elimination yields the less substituted alkene, we say that it follows the ________ rule

A

When an elimination yields the less substituted alkene, we say that it follows the hofmann rule

40
Q
A

CHEM 264 Organic Chemistry (5 decks)

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