EXPERIMENT #6

Question 1

general molecular formula of Carbohydrates

Answer 1

Cn(H2O)n

Question 2

Carbohydrates were once considered

Answer 2

hydrates of carbon.

Question 3

Simplest carbohydrates

Answer 3

Monosaccharides

Question 4

• monosaccharides, which can either be

Answer 4

Polyhydroxy aldehyde
Polyhydroxy ketones

Question 5

general structure B

Answer 5

Ketoses

Question 6

Polyhydroxy aldehyde (general structure A)

Answer 6

Aldoses

Question 7

monosaccharide usually consists of how many carbons?

Answer 7

3-6 carbons.

Question 8

Examples of monosaccharides are

Answer 8

ribose, glucose and fructose.

Question 9

monosaccharides exist in what from?

Answer 9

Cyclic form - the aldehyde and ketone

Question 10

the aldehyde or ketone group reacts with one of the -OH groups on the other end of the same molecule to form what?

Answer 10

cyclic hemiacetal

Question 11

2 different anomers

Answer 11

A-D-Glucose
B-D-Glucose

Question 12

What is a disaccharide?

Answer 12

Two monosaccharides may be combined with the loss of one molecule of water to form a disaccharide.

Question 13

The bond that connects 2 monosaccharide units in a disaccharide is known as

Answer 13

Glycosidic bond

Question 14

Ex. Do disaccharides

Answer 14

Sucrose (sugar)
Lactose’s (milk sugar)

Question 15

consists of many monosaccharides linked together.

Answer 15

Polysaccharides

Question 16

examples of polysaccharides:

Answer 16

Starch
Pectin
Glycogen
Cellulose

Question 17

Qualitative detection of carbohydrates in solution is usually done in the laboratory using what test

Answer 17

Molisch’s test

Question 18

Reagent if Molisch’s test

Answer 18

Concentrated (H2SO4) Sulfuric acid
Molisch’s reagent

Question 19

carbohydrate that is oxidized by a weak oxidizing agent in basic aqueous solutions,

Answer 19

Reducing sugar

Question 20

Not oxidized

Answer 20

Non-reducing sugar

Question 21

• All aldoses are the true reducing sugars

Answer 21

They contain the aldehyde functional group

Question 22

Why Ketoses do not contain aldehyde?

Answer 22

They contain ketones

Question 23

Ketoses shows reducing properties, how?

Answer 23

In basic aqueous solution, undergo keto-whole tautomerizatiojn converting them to mixture of aldoses

Question 24

All monosaccharides are reducing sugar or non- reducing sugar?

Answer 24

Reducing sugar

Question 25

What disaccharides that are reducing?

Answer 25

Those that contains free anomeric carbon

Question 26

What’s with the free anomeric carbon?

Answer 26

Has the capacity to open and expose the aldehyde group

Question 27

several weak oxidizing agents that can be used to determine whether a carbohydrate is reducing or not, such as

Answer 27

 Benedict's reagent  Fehling's reagent  Tollen's reagent  Nylander's reagent  picric acid with sodium carbonate solution.

Question 28

What is common to all weak oxidizing reagents

Answer 28

Ph under 7 (basic)

Question 29

All the test for carbohydrates

Answer 29

Molisch’s test Benedict’s test Picric acid test Mooore’s test Barfoed’s test for monosaccharides Seliwanoff test for ketoses Bial’s test for pentoses Iodine’s test for polysaccharides

Question 30

can also be used to quantitatively estimate the amount of sugar in a solution. This is also used to detect glucose in the urine.

Answer 30

Benedict’s test

Question 31

PT of Benedict’s test

Answer 31

Brick red precipitate (large amount of sugar Orange red pot. (Moderate) Green/yellow pot ( traces of reducing sugar) Blue solution (no sugar)

Question 32

Benedict's test reagent.

Answer 32

Benedicts reagent

Question 33

A positive test is evidenced by the formation of a (Benedicts test)

Answer 33

brick red precipitate of cuprous oxide (Cu₂O),

Question 34

Positive result is indicated by the formation of mahogany red colored solution which is due to the reduction of picric acid to picramic acid.

Answer 34

Picric acid test

Question 35

Oxidizing agent of picric acid test

Answer 35

Picric acid solution

Question 36

Picric acid test’s reagent

Answer 36

saturated picric acid solution followed by 0.5 mL of 10% Na2CO3, solution.

Question 37

is used to distinguish aldoses from ketoses

Answer 37

Seliwanoff's Test for Ketoses

Question 38

dehydrates ketoses more rapidly to give furfural derivatives.

Answer 38

Seliwanoff's reagent

Question 39

The resultant furfural derivatives undergo condensation reaction with___________ present in the reagent to give cherry red complex

Answer 39

Resorcinol

Question 40

When a reducing sugar reacts with picric acid, it is converted into its corresponding

Answer 40

Aldonic acid and mahogany red ppt (picramic acid )

Question 41

when reducing sugars are boiled with concentrated sodium hydroxide,

Answer 41

Moores TEST

Question 42

Moores test undergo what?

Answer 42

aldol condensation to form a resinous substance, a caramel.

Question 43

PT MOORES TEST

Answer 43

Caramel with brown color

Question 44

This test is used for distinguishing monosaccharides from reducing disaccharides.

Answer 44

Barfoed test

Question 45

PT of Barfoed test

Answer 45

Brick red color