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1

Why are esters more stable than ketones and aldehydes?

Esters have a conjugated system

2

Why does oxidation of an ester require 2 equivalents of organometallic?

the -OCH3 leaving group will depart and a ketone will form

the ketone is more reactive than an ester, so the reaciton will happen again

3

What is the least electrophilic carbonyl in oxidation?

amide

4

Why is an amide the least electrophilic carbonyl in oxidation?

It has the most basic pair of electrons

These electrons contribute to competing resonance the most and "go into" the pi-system

This reduces the electrophilicity of the carbonyl

5

What is the most reactive carbonyl in nucleophilic acyl substitution?

Amide> acid anhydride> amide

Have good leaving group so reactive for nucleophilic acyl substitution because a leaving group will leave

6

When are metal hydrides used?

Metal hydrides are used to reduce a carbon

7

Examples of metal hydrides

NaBH4

LiAlH4

8

Why is LiAlH4 a stronger reducing agent?

LiAlH4 is a stronger reducing agent because of it higher HOMO since Al is less electronegative than B

Also Al is bigger so it able to better take extra electrons

9

Do reducing agents act as nucleophiles or electrophiles?

Reducing agents act as nucleophiles

10

What happens when carbon is oxidized?

When carbons are oxidized they lose electrons

Ex: Alcohol to ketone (+1 to +2 = losing electrons)

11

What metal hydride do we need to use to reduce an ester?

We need to use LiAlH4 to reduce an ester

Since esters are conjugated they require a stronger metal hydride in order to be reduced

12

What metal hydride do we need to use to reduce an ester?

We need to use LiAlH4 to reduce an ester

Since esters are conjugated they require a stronger metal hydride in order to be reduced

13

What molecule is used to oxidize an organic molecule?

Use CrO3

Remember: oxidation is loss (going from alcohol to ketone)

14

What does chromate oxidation of a 1º alcohol produce?

a carboxylic acid

15

How does chromate oxidation of a 1º alcohol produce a carboxlyic acid?

through a hydrate intermediate

16

Ozone molecule structure

a 1,3-dipole through resonance

one end of the molecule has a positive charge and one end has a negative charge

17

What is the pi-system of ozone?

3 psi orbitals

HOMO: psi-2 (non-bonding node in the middle)
LUMO: psi-3

18

What are the interacting orbitals in ozonolysis?

Either O3 LUMO and piCC

Or O3 HOMO and pi*CC

(both homo lumo sets occur)

19

Why is the primary ozonide less stable than secondary ozonide?

the primary ozonide has 2 unstable o-o bonds

the secondary ozonide only has 1 unstable o-o bond

20

When does workup matter?

Workup matters in ozonlysis

21

Oxidative workup

H2O2

Will turn aldehydes into carboxylic acid

22

Reductive workup

Me2S

Aldehydes will remain aldehyde

23

Hydrogenation

Turns alkene into alkane

24

Reactants of hydrogenation

1) Alkene
2) H2
3) Metal (Pd or Pt)

25

Stereoselectivity of hydrogenation

H2 will attack syn

26

Why is a metal needed for hydrogenation?

Homo/lumo of H2 can line up with the metal's d-orbital

27

What is the energy required to go from an butene to an butane with H2?

28.6 kcal/mol

28

What is the energy required to go from 1,3-butadiene to two alkanes?

55.4 kcal/mol

(not just two times 28.6 kcal/mol since the system is conjugated)

29

hemiacetal

two -OH groups on same alcohol

unstable intermediate

30

What does CrO3 allow for?

Oxidation of alcohol (alcohol to ketone)