Organic Chemistry II Lab Final

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1

What is the electrophile in a Friedel-Crafts reaction?

carbocation

2

How is the alkyl electrophile formed during Friedel-Crafts alkylation?

Lewis acid catalyst is used to remove the halogen from an alkyl halide, creating a cation which is then attacked by the pi electrons in the aromatic system.

3

How is the aromatic ring reformed during the electrophilic aromatic substitution using Friedel-Crafts alkylation and acylation?

water or the conjugate base of the acid catalyst attacks the hydrogen on the same carbon as the substituent being added, causing the electrons to fall back into the ring

4
  • Rearrangement of substituents
  • Polysubstitution
  • Cannot use vinyl halides
  • Cannot be performed on deactivated ring

These are all drawbacks of:

Friedel-Crafts alkylation

5

CN, HOSO2, NO2 act as what kind of substituents on a benzene ring? What effect does this have on substituents being added to the ring? Are halogens considered part of this group?

deactivating, withdraws electron density from ortho positions causing the substituents to direct to the meta position preferentially, halogens are considered deactivating bc they are slower than benzene but you can perform Friedel-Crafts on a halobenzene and it will direct ortho-para.

6

What can cause a substituent to prefer the para position over the ortho position?

steric hindrance

7

In the nitration of methyl benzoate, how is the nitronium ion intermediate formed?

nitric acid is protonated by the sulfuric acid catalyst, which causes the formation of a small, stable leaving group: water

8

What effect does temperature have on nitration products?

an increase in temperature correlates to an increased number of additions to a benzene ring. To obtain a monosubstituted product, the reaction must take place at cold temperatures.

9

What is the relationship between borneol and isoborneol?

diastereomers

10

How is camphor able to form two stereoisomers?

planar geometry of the C=O double bond allows it to be attacked from above and below

11

A bottom-side attack of camphor using sodium borohydride will cause the ___________ isomer to form.

Isoborneol

12

A top-face attack of camphor using sodium borohydride will cause the ___________ isomer to form.

Borneol

13

Isoborneol is converted to camphor by _____________ using sodium hypochlorite.

oxidation

14

What mechanism is used to oxidize isoborneol to camphor?

E2 elimination

15

How many chiral centers do isoborneol and borneol possess respectively?

3

16

What is the chiral conformation of borneol?

R,S

17

What is the chiral conformation of isoborneol?

R,R

18

In order to perform the oxidation of camphor using household bleach, what was done to sodium hypochlorite (NaOCl)?

it was converted to the oxidizing agent hypochlorous acid using glacial acetic acid

19

What is considered the nucleophile in a Grignard reagent

the carbon attached to the magnesium

20

Nucleophiles are Lewis _________.

bases

21

What does the carbon nucleophile in a Grignard reagent attack?

the partially positive carbon in the C=O bond

22

Why is it so important to perform a Grignard Reaction using anhydrous conditions?

carbon nucleophiles are aggressive and will react with atmospheric moisture to form MgBrOH

23

The purpose of HCl in Grignard reactions is to

protonate the oxygen on the product to form an alcohol

24

What test is performed to detect the presence of an aldehyde?

Tollen's test

25

What test is performed to detect the presence of a methyl ketone?

Iodoform test

26

What aldehyde will produce a positive Iodoform?

ethanal, also known as acetaldehyde

27

The iodoform reaction proceeds via

alpha elimination

28

What reaction uses: Ag(NH3)2 under basic conditions?

Tollen's test

29

In Iodoform reactions, what does iodine substitute?

all 3 alpha hydrogens on the methyl group

30

What does a positive Iodoform test produce?

bright yellow precipitate

31
card image

What is this compound called?

imine

32

What is the function of the acid catalyst in imine formation?

the elimination of water to form the double bond between carbon and nitrogen.

33

What happens if you use NHO3 and H2SO4 on an aniline ring?

the lone pair on the NH2 group is a Lewis base and will react with the Lewis acid catalyst

34

True or False: it is ok to add boiling chips to a round bottom flask that is already being heated

False

35

True or False: If a chemical is splashed on your face, remove your goggles before washing

False

36

What is the purpose of reflux?

allows the reaction to be heated at the boiling point of the reactants which increases the overall rate of the ration without loss of product from evaporation, potentially increasing the overall yield

37

What is the purpose of distillation?

uses a condenser to collect and isolate a pure product from a mixture of reactants based on differences in boiling points

38

What is the purpose of reacting an aldehyde/ketone with semicarbazone or 2,4-DNP?

convert liquid aldehydes and ketones to a solid for the purposes of melting point comparison

39

Semicarbazide possesses two -NH2 groups, one that is alpha to the carbonyl carbon (C=O) and one that is beta. Why is the alpha group less reactive?

electrons are tied up in resonance with the carbonyl group

40

Why is the carbanion formed during aldol condensation stable?

resonance structure called an enolate

41

What reagent is used to form the enolate during aldol condensation and what does it attack?

NaOH, alpha hydrogens

42

Why do aldol products that form from aromatic aldehydes/ketones spontaneously dehydrate?

because they are conjugated and extremely stable

43

How do you avoid creating the Cannizarro side product that is sometimes formed during an aldol condensation?

combine the reactants together before adding base so that benzaldehyde does not react with it

44

What does the excess benzaldehyde react with during a Cannizarro side product formation of an aldol condensation, and what does it form?

NaOH, benzoic acid and benzyl alcohol

45

What is Fisher Esterification?

the acid-catalyzed and reversible reaction between a carboxylic acid and an alcohol to create an ester

46

According to LeChatelier's Principle, how would you tip the reversible Fisher Esterification reaction toward the formation of product?

removal of product as it is formed, heating the solution, and increasing the concentration of the reactants

47

What is the role of acetic acid and sulfuric acid in Fischer Esterification?

acetic acid is the carboxylic acid and sulfuric acid is the catalyst. When combined they form a carbocation that will react with alcohol. Sulfuric acid also serves to remove the water byproduct, shifting the equilibrium in favor of the products

48

What is the purpose of washing the Fisher Esterification product in sodium bicarbonate?

its a weak base which will quench any excess acid to its conjugate base (a salt) which will precipitate out as a solid and can be easily removed

49

What can you calculate using this equation?

[(2xC+2)+N-H-X] / 2

degrees of unsaturation

50

What kind of spectroscopy can be used to determine functional groups?

IR spectroscopy

51

The number of signals (peaks) in Proton-NMR is equivalent to the number of individual or sets of

unique hydrogens

52

The __________ reflects the number of H's associated with a particular peak

integration

53

Ppm, or parts per million, corresponds with bond polarity. It is also called

chemical shift

54

What will have a Carbon NMR peak in the 200 ppm range?

C=O

55

What is generally considered the aliphatic range for Carbon NMR?

20-140 ppm

56

What is generally considered the aromatic range for Carbon NMR?

110-170 ppm

57

What is generally considered the C-X or C-O range for Carbon NMR?

45-90 ppm

58

What is generally considered the COOH range for Proton NMR?

9.8-13 ppm

59

What is generally considered the aldehyde range for Proton NMR?

9-10 ppm

60

What is generally considered the aromatic range for Proton NMR?

6.5-8.5 ppm

61

What is generally considered the amine range for Proton NMR?

0.7-2.7 ppm

62

What is generally considered the ~OH range for Proton NMR?

1-5 ppm

63

What is generally considered the C-O,C-X,C-NR2 range for Proton NMR?

2.5-4.3 ppm

64

What is generally considered the amide range for Proton NMR?

5-8 ppm

65

What is generally considered the alkene range for Proton NMR?

4.4-7 ppm

66

What is generally considered the ketone range for Proton NMR?

2-3 ppm

67

What groups will have the highest Proton NMR chemical shifts?

carboxylic acids and aldehydes

68

What 3 clues can Proton NMR give about the structure of an unknown?

chemical shift provides functional group clues, N+1 (splitting pattern) can give connectivity clues, and integration can determine the number of unique hydrogens

69

How many degrees of unsaturation does an aromatic ring have?

4

70

What type of functional group will have an IR peak at 1700?

C=O

71

Where will aromatic ring peaks show up on IR?

1500-1600

72

Where will N-H (amine) groups show up on IR?

3300-3500

73

An aldehyde will have twin peaks at ______ and ______ and a long, stretched out peak at ______.

2700, 2800, 1700

74

C-H bonds in aromatic rings will have IR peaks around

3000-3100

75

Where will nitriles (C triple bonded to N) show up on IR?

2200

76

What is considered the aliphatic range of Proton NMR?

1-4.5 ppm

77

What is considered the aromatic range of Proton NMR?

6.5-8.5 ppm

78

A Wittig reaction uses a strong base (such as NaOH) to pull a proton off of the carbon attached to the Ph3P group (triphenylphosphine) group. This creates the nucleophile, otherwise known as

an ylide

79

In a Wittig reaction, a nucleophilic ylide is formed which will attack

the partially positive carbon in a C=O bond