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2023-2024 > Organic II - Conjugation Systems (Chp 15) > Flashcards

Organic II - Conjugation Systems (Chp 15) Flashcards

1
Q

When does conjugation occur?

A

Whenever p orbitals can overlap on 3 or more adjacent atoms.

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2
Q

Conjugated double bonds are separated by a _________ bond.

A

single

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3
Q

Isolated double bonds are separated by ________________ bonds.

A

2 or more single

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4
Q

Conjugated double bonds are _____ stable than other bonds.

A

more

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5
Q

Conjugated double bonds have extra ______.

A

stability

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6
Q

The more stable the compound, the less heat released during _____________.

A

hydrogenation

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7
Q

How many lobes does each p orbital have with the wave function?

A

2 lobes

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8
Q

How many p orbitals does 1,2-dibutene have?

A

4 p orbitals (atomic orbitals)

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9
Q

When lobes overlap constructively, what is formed?

A

A pi bonding (p) MO is formed

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10
Q

Even number of MOs leads to an…

A

even number of bonding and antibonding MOs.

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11
Q

The number of atomic orbitals equals…

A

the number of molecular orbitals (MO).

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12
Q

Odd number of MOs means there are…

A

bonding, antibonding and a bonding MO.

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13
Q

The maximum number of nodes equals…

A

n-1 (n = number of atomic orbitals)

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14
Q

What creates nodes?

A

Antibonding

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15
Q

Which is more stable, s-trans or s-cis? Why?

A

s-trans b/c it has no interference b/w protons.

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16
Q

Describe an allylic carbon.

A

The carbon directly attached to an sp2 carbon (double bonded carbon).

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17
Q

Which is more stable? s-trans or s-cis?

A

s-trans

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18
Q

Molecules with resonance structures are more ______ than those that don’t.

A

stable

19
Q

List the order of stability for carbocations.

A

CH3+ < primary < secondary, primary allylic < tertiary, secondary allylic

20
Q

Which forms faster? Kinetic product or the thermodynamic product?

A

Kinetic product.

21
Q

List the radical stabilities.

A

1 < 2 < 3 < 1 allylic

22
Q

NBS provides a low, _________ concentration of ___.

A

constant; Br2

23
Q

NBS reacting with HBr by-product to produce Br2 to prevent what?

A

HBr addition across the double bond.

24
Q

Are there any bonding interactions when there are only nodes?

A

No.

25
Q

Diel-Alder reactions produces a ____.

A

ring

26
Q

How many steps does diels-alder reactions take?

A

One.

27
Q

What two reactants are needed in Diel-Alder reactions?

A

A diene and a dienophile.

28
Q

The diene in Diels-Alder reactions need to be in ___ conformation.

A

cis

29
Q

Dienes like to react with an ____________ alkene to give cyclohexene or cyclohexadiene rings.

A

electron-poor

30
Q

Why is a 1,3-cyclopentadiene more stable than 2,3-butadiene?

A

Because the double bonds are fixed in the cyclic compound and is in cis conformation.

31
Q

For Diels-Alder rxc, diene must be in ____ conformation.

A

s-cis

32
Q

For Diel-alder reactions, what of kind of products will you always get?

A

1,2- and 1,4-product

33
Q

What are the steps to finding a diene and dienophile? (3 steps)

A

1) Find the 6 C ring with double bond
2) Draw the 3 arrows starting from the pi bond
3) Draw the diene and dienophile

34
Q

What does pericyclic reaction mean?

A

Everything happens in one step.

35
Q

What is an example of a pericyclic reaction?

A

Diels-Alder reaction

36
Q

MOs must overlap ____________ to stabilize the ____________ state in pericyclic reactions.

A

constructively; transition

37
Q

An energy gap in ultraviolet spectroscopy is _______ with conjugated dienes than other dienes.

A

higher

38
Q

The lower the energy, the ________ the wavelength.

A

longer

39
Q

What does the spectrometer measure?

A

The intensity of a reference beam through solvent only (Ir) and the intensity of a beam through a solution of the sample (Is)

40
Q

What law does absorbance follow?

A

Beer’s Law

41
Q

Give the formula for absorbance.

A

A = εcl
ε - molar absorptivity
c - sampel concentration in moles per liters
l - length of light path in cm

42
Q

The more conjugation, the ________ the wavelength, and the ________ the gap between MOs.

A

longer; smaller

43
Q

To see if a reaction is photochemically produced what must happen?

A

The HOMO+ of diene and LUMO of dienophile must be bonded on both sides.

2023-2024 (16 decks)

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