Aldehydes, Ketone, and Carbohydrates

Question 1

ketones and aldehydes with fewer than five carbon atoms are soluble in water and form neutral solutions (pH = 7)
True or False

Answer 1

True

Question 2

Aldehydes and ketones with 5<C<9 are soluble in water, 5% NaOH and 5% HCL but soluble in concentrated H2SO4 (Class N)
True or False

Answer 2

False (They are insoluble in water)

Question 3

2,4 - DNP Test are test for aldehydes and ketones
True ore False

Answer 3

True

Question 4

2,4 - DNp Test reagent

Answer 4

2,4 - dinitrophenylhydrazine

Question 5

Positive Result: Formation of yellow or orange-red precipitate

Answer 5

2,4 - DNp Test reagent

Question 6

General test for the presence of the carbon-oxygen double bond.

Answer 6

2,4 - DNp Test reagent

Question 7

Formation of an orange or yellow precipitate from a carbon-oxygen double bond in an aldehyde or ketone

Answer 7

2,4 - DNp Test reagent

Question 8

It help to identify the specific aldehyde or ketone (recrystallization, purification, and MP determination)

Answer 8

2,4 - DNp Test reagent

Question 9

Complications: some ketones give oils which will not solidify, some allylic alcohols are oxidized by the reagent to aldehydes and ketones and give positive results; some not pure alcohols may contain aldehyde or ketone impurities.

Answer 9

2,4 - DNp Test reagent

Question 10

A C-H bond on the a-carbon to a carbonyl group is more acidic than many other C-H bonds, because reaction with base forms a resonance - stabilized enolate anion.

Answer 10

Haloform Reaction

Question 11

Enolates are ________, and so they react with _______ to form new bonds on the a-carbon.

Answer 11

nucleophiles and electrophiles

Question 12

Halogenation of methyl ketones in base to form ______. (Haloform Reaction)

Answer 12

iodoform (HCl3)

Question 13

In the haloform reaction, the reaction occurs with methyl ketones and results in cleavage of a carbon-carbon σ bond.
True or False

Answer 13

True

Question 14

Iodoform Test for Methyl Ketone is test for acetaldehyde and methyl ketones
True or False

Answer 14

True

Question 15

Positive result: formation of a yellow precipitate or suspension of iodoform and a distinct smell

Answer 15

Iodoform Test for Methyl Ketone

Question 16

Complication: The reaction also gives a positive result with secondary alcohols of the type RCH(OH)CH3 because they are oxidized under the reaction conditions to methyl ketones.

Answer 16

Iodoform Test for Methyl Ketone

Question 17

Oxidation - Aldehydes are readily oxidized to carboxylic acids whereas ketones cannot be readily oxidized (under acidic conditions) True or False

Answer 17

True

Question 18

This difference (oxidation) forms the basis of the tests for distinguishing aldehydes and ketones
True or False

Answer 18

True

Question 19

Under alkaline condition, a ______ is formed instead

Answer 19

salt

Question 20

Tollen’s Test is test for aldehydes
True or False

Answer 20

True

Question 21

reagent: Ammoniacal silver nitrate

Answer 21

Tollen’s Test

Question 22

Positive Test: formation of elemental silver, accumulated onto the inner surface of the reaction vessel, producing a silver mirror in the inner surface of the vessel

Answer 22

Tollen’s Test

Question 23

Complications: The tube must be clean and oil-free if a silver mirror is to be observed.

Answer 23

Tollen’s Test

Question 24

In Tollen’s Test, Aromatic amine and some phenols are easily oxidized which give a positive results
True or False

Answer 24

False (it gives a false positive result)

Question 25

Fehling's Test is a test for ketones True or False

Answer 25

False (it is a test for aldehydes)

Question 26

Reagent: Fehling's solution A (CuSO4) and Fehling's solution B (sodium potassium tartrate or Rochelle salt and strong alkali - NaOH)

Answer 26

Fehling's Test

Question 27

Positive results: formation of red precipitate (cuprous oxide)

Answer 27

Fehling's Test

Question 28

Purpald Test reacts with aldehydes to form a cyclic derivatives True or False

Answer 28

True

Question 29

Reagent: 4-amino-5-mercapto-1,2,4-triazole (heterocyclic compounds)

Answer 29

Purpald Test

Question 30

In Purpald Test, the cyclic derivative is then _________ by exposure to air and forms an intensely colored (usually purple) product.

Answer 30

oxidized

Question 31

Jones Test is a test for ketones

Answer 31

False (test for aldehydes)

Question 32

Reagent: CrO3/H2SO4

Answer 32

Jones Test

Question 33

Positive Results: disappearance of orange color (Jone's reagent) and appearance of greenish precipitate

Answer 33

Jones Test

Question 34

In Jones Test, ________ are rapidly oxidized to carboxylic acids

Answer 34

Aldehydes

Question 35

Complication: The color usually develops in 5-15 seconds

Answer 35

Jones Test

Question 36

Schiff's Test is a test for aldehydes True or False

Answer 36

True

Question 37

reagent: Schiff's reagent

Answer 37

Schiff's Test

Question 38

Positive results: appearance of pink or magenta color

Answer 38

Schiff's Test

Question 39

m-dinitrobenzene Test is a test for ketones True or False

Answer 39

True

Question 40

Reagent: m-dinitrobenzene

Answer 40

m-dinitrobenzene Test

Question 41

Positive results: appearance of violet color

Answer 41

m-dinitrobenzene Test

Question 42

Rothera's Test is a test for aldehydes True or False

Answer 42

False ( for ketones)

Question 43

Reagent: sodium nitroprusside in alkaline medium

Answer 43

Rothera's Test

Question 44

Positive results: appearance of red color complex

Answer 44

Rothera's Test

Question 45

It is the polyhydroxy aldehydes or ketones or substances that hydrolyze to yield polyhydroxy aldehydes and ketones

Answer 45

Carbohydrates

Question 46

Aldehydes and ketones are simple compounds which contain a _________ - a carbon-oxygen double bond.

Answer 46

carbonyl group

Question 47

The carbonyl group has a hydrogen atom attached to it together with either: - a second hydrogen atom or - a hydrocarbon group which might be an alkyl group or one containing a benzene ring.

Answer 47

Aldehydes

Question 48

The carbonyl group has two hydrocarbon groups attached.

Answer 48

Ketones

Question 49

reagent: I2/NaOH

Answer 49

Iodoform Test for Methyl Ketone

Question 50

consist of 3-7 C atoms. classified as either aldoses or ketoses ketoses

Answer 50

Monosaccharides (Simple Sugars)

Question 51

two monosaccharide units linked by a glycosidic bond. Classified as reducing or non-reducing disaccharides

Answer 51

Disaccharides

Question 52

consist of ten to thousands of monosaccharide units

Answer 52

Polysaccharides

Question 53

Benedict’s Test is a test for reducing sugars True or False

Answer 53

True

Question 54

positive result: formation of yellow, yellow-green, orange or brick-red precipitate

Answer 54

Benedict’s Test

Question 55

Reagent: Benedict’s Reagent

Answer 55

Benedict’s Test

Question 56

Reduction test for carbohydrates

Answer 56

Benedict’s Test

Question 57

The free aldehyde or keto group in the reducing sugars reduce cupric hydroxide in alkaline medium to red colored cuprous oxide. True or False

Answer 57

True

Question 58

Depending on the _______ of ________, yellow to green color is developed

Answer 58

concentration of sugars

Question 59

All _________ are reducing sugars as they all have a free reactive carbonyl group.

Answer 59

monosaccharides

Question 60

Some disaccharides, i.e. reducing disaccharides, have exposed carbonyl groups but less reactive than monosaccharides True or False

Answer 60

True