carbs powerpoint (lab)

Question 1

Molisch’s Test named after…?

Answer 1

Austrian botanist Hans Molisch

Question 2

molischs test for the presence of _________________

Answer 2

carbohydrates

Question 3

Reagents: A solution of naphthol in ethanol (95%)
* Sample: 2ml of 5% solution s of glucose, sucrose and starch

Answer 3

Molisch’s test

Question 4

A positive
reaction is indicated by appearance of a PURPLE RING at the interface between the acid
and test layers.

Answer 4

Molisch’s test

Question 5

Glycosidic bonds are hydrolyzed by conc. H2SO4, producing monosaccharides, dehydrated to furfural-forming substances — a
negative result is a good evidence of the absence of carbohydrates.

Answer 5

Molisch’s test

Question 6

All carbohydrates – monosaccharides,
disaccharides, and polysaccharides – should
give a positive reaction

Answer 6

Molisch’s test

Question 7

Reagent: NaOH (used to neutralize citric acid added for
hydrolysis)
* Sample: 1 ml of 5% glucose solution
1 ml of 5% sucrose solution
1 ml of 5% starch solution
Boiled and note the odor and color

Answer 7

Moore’s Test

Question 8

Test is based on the liberation of aldehyde
A positive result will give a brown color with caramel like odor

Answer 8

Moore’s Test

Question 9

• Sucrose negative result (no free aldehyde group), Colorless
• Glucose and Starch positive result

Answer 9

Moore’s Test

Question 10

The Anthrone test is another general test for…?

Answer 10

carbohydrates

Question 11

The H2SO4 hydrolyses
bound sugars to yield furfural or furfural derivatives. This reacts with __________ to form
colored compounds.

Answer 11

anthrone

Question 12

Sample: 1 ml of 5% glucose solution, 1 ml of 5% sucrose solution, 1 ml of 5% starch
solution
Positive Result: Bluish green complex
All

Answer 12

anthrone test

Question 13

The furfural or hydroxyfurfural formed condenses with two molecules of
napthol from anthrone reagent to form a ____-______ complex.

Answer 13

blue-green

Question 14

Anthrone test and Molisch test are two types of _________ tests.

Answer 14

analytical

Question 15

key difference between Anthrone and Molisch test

Answer 15

anthrone: detect carbs in blue-green
molisch: detect carbs in violet

Question 16

formation of a crystalline dicarboxylic acid that is insoluble in dilute HNO3 (Nitric
Acid);
reaction unique for galactose and galactose compounds.

Answer 16

Mucic acid test

Question 17

______ Acid – (colorless) catalyzes the hydrolysis of lactose to glucose and galactose, then oxidizes
both sugars to the _________________ acids (mucic acid crystals)

Answer 17

Nitric; tetrahydroxy

Question 18

Specific test for galactose

Answer 18

Mucic acid test

Question 19

Results: Galactose - white sandy precipitate
□ Lactose -white flakes precipitate
□ Glucose - Negative

Answer 19

Mucic acid test

Question 20

(Theodor Seliwanoff)

Answer 20

Seliwanoff ’s Test

Question 21

_______ is a chemical product resulting from the hydrolysis of pentoses

Answer 21

Furfural

Question 22

Ketoses undergo dehydration to yield furfural derivatives more rapidly than aldoses, and form
complexes with resorcinol which are colored.

Answer 22

Seliwanoff ’s Test

Question 23

Test to distinguish aldose (-) from ketose (+)
- Specific test for fructose
- Useful for detecting the presence of ketose

Answer 23

Seliwanoff ’s Test

Question 24

Results:
- Sucrose and Fructose ⇛ Red/Cherry Red
- Lactose, Maltose, Glucose and Galactose ⇛ yellow

Answer 24

Seliwanoff ’s Test

Question 25

Why should glucose and maltose give positive results upon prolonged boiling with seliwanoff’s Reagents?

Answer 25

* The high concentration of glucose or other sugar may interfere by producing similar colored compounds with seliwanoff’s reagent.

Question 26

(Seliwanoff's Test) Prolonged boiling can transform __________ to __________ by catalytic action of acid and form cherry red complex giving a false- positive result.

Answer 26

glucose to fructose

Question 27

* A color reaction that is specific for pentoses.

Answer 27

BIAL’S TEST

Question 28

(Bial's test) It involves the decomposition of these sugars when heated with conc. HCl (dehydrating agent) to furfural, which condenses with orcinol (3,5- dihydroxytoluene) to form _________ to _________ colored compounds.

Answer 28

blue to green

Question 29

Sample: 5% ribose, glucose, fructose, galactose, maltose, lactose, sucrose * Reagents: Orcinol, conc. HCl, Ferric chloride * Result: - Positive: Ribose (Pentose, 5 carbons)

Answer 29

Bial's test

Question 30

Detecting Dextrin from Starch

Answer 30

IODINE TEST

Question 31

Iodine Test for Starch

Answer 31

deep blue

Question 32

(Iodine test) Preparation of Dextrin from starch

Answer 32

violet

Question 33

(Iodine test) Gum Arabic ( a non-digestible carbohydrate) with Iodine

Answer 33

No blue or red-brown color

Question 34

(Iodine test) Agar-agar (starch) with Iodine –

Answer 34

dark brown color

Question 35

- a galactose based heterogenous polysaccharide derived from algae

Answer 35

Agar-agar (starch)

Question 36

is a REDUCITON chemical test used to differentiate between water-soluble aldehyde and ketone functional groups,

Answer 36

Fehling's Test

Question 37

The REDUCTION test was developed by German chemist Hermann von Fehling in 1849.

Answer 37

Fehling's Test

Question 38

Fehling's A is a _____ _________ solution of copper(II) sulfate

Answer 38

blue aqueous

Question 39

Fehling's B is a _____ solution of aqueous potassium sodium tartrate (also known as Rochelle salt) and a strong alkali (commonly sodium hydroxide).

Answer 39

clear

Question 40

Equal volumes of the two mixtures are mixed together to get the final Fehling's solution, which is a deep _______ color

Answer 40

blue

Question 41

A positive result is indicated by the formation of a brick red precipitate

Answer 41

fehling's test

Question 42

All sugar solutions produced a Brick red ppt except: - Sucrose- Blue solution

Answer 42

fehling's test

Question 43

sugars that doesn't have any free ketone or aldehyde groups

Answer 43

NON- REDUCING SUGARS

Question 44

is sucrose a non-reducing sugar?

Answer 44

yes

Question 45

like glucose and lactose, have free ketone or aldehyde functional groups, which enable the formation of a hemiacetal

Answer 45

reducing sugars

Question 46

Benedict's Test

Answer 46

test for the presence of reducing sugars.

Question 47

determines the presence of non-reducing sugars in a test solution.

Answer 47

Benedict's Test for non-reducing sugars

Question 48

(benedict's test) - copper(II) sulphate/cupric sulfate - sodium carbonate - sodium citrate

Answer 48

The principal reagent in Benedict's Test for Reducing Sugars

Question 49

(benedict's test) sugars which do not have an aldehyde or a keto functional group - the reducing species

Answer 49

Non-reducing sugars

Question 50

(benedict's test) The absence of the aldehyde or keto group, cannot reduce ______ (__) (blue) to the _______ (__) (red).

Answer 50

copper (II); copper(I)

Question 51

(benedict's test) Sucrose is the most common disaccharide ___-___________ sugar.

Answer 51

non-reducing

Question 52

A Positive test produced a BRICK RED PRECIPITATE. - (from blue to green to yellow to orange to brick red)

Answer 52

benedict's test

Question 53

used to test forthe presence of glucose in urine.

Answer 53

benedict's test

Question 54

TRUE/FALSE? Only glucose is indicative of diabetes.

Answer 54

TRUE

Question 55

presence of reducing sugars.

Answer 55

NYLANDER’S TEST

Question 56

- Indicated by the formation of a dark brown to black precipitate - all sugars are positive except for Sucrose

Answer 56

NYLANDER’S TEST

Question 57

Yellow color; Reducing sugars will give a mahogany red color due to the formation of sodium picramate

Answer 57

Picric acid test

Question 58

detecting the presence of monosaccharides from disaccharides.

Answer 58

Barfoed's test

Question 59

invented by Danish chemist ________ _________ Barfoed and is primarily used in botany

Answer 59

CHRISTEN THOMSEN

Question 60

Disaccharides may also react, but the reaction is much slower.) thus they produced a negative results (blue solution) Monosaccharides produced a brick red precipitate.

Answer 60

BARFOED

Question 61

What product is formed when picric acid is reduced?

Answer 61

Sodium picramate