Experiment #7: Aldehydes And Ketones Flashcards
IDENTIFICATION:
Aldehydes and Ketones with ____________ are soluble in water and form neutral solutions (pH=7)
fewer five atoms
It is the general test for aldehydes and ketones
2,4 - DNP Test
What is the reagent for 2,4-DNP test?
2,4 - dinitrophenylhydrazine
What is the positive result of 2,4 - DNP Test?
Formation of orange-yellow or orange-red precipitate from a carbon-oxygen double bond in an aldehyde or ketone
TRUE OR FALSE
Ketones are readily oxidized to carboxylic acids whereas Aldehydes cannot be readily oxidized under acidic conditions
FALSE; Aldehydes are readily oxidized while Ketones cannot be readily oxidized under acidic conditions
What is the test for aldehydes where the reagent is Ammoniacal Silver Nitrate?
Tollen’s Test
What is the positive result for Tollen’s Test?
Formation of elemental silver, accumulated onto the inner surface of the reaction vessel, producing silver mirror on the inner surface of the vessel
It is test for aldehydes where the reagent is Fehling’s solution A (CuSO4) and Fehling’s solution B (sodium potassium tartrate or Rochelle salt and stong alkali - NaOH)
Fehling’s Test
What is the positive result for Fehling’s Test?
Formation of red precipitate (cuprous oxide)
It is a test for aldehydes where the reagent is 4-amino-5-mercapto-1,2,4-triazole (heterocyclic compound)
Purpald Test
Purpald Test reacts with aldehydes to form a ____________?
Cyclic Derivative
TRUE OR FALSE:
When react with the reagent, the cyclic derivative is then oxidized by exposure to air and forms an intensely colored (usually purple) product.
TRUE
It is a test for aldehydes where the reagent is CrO3/H2SO4
Jones Test
What is the positive result for Jones Test?
disappearance of orange color (Jones’ reagent) and appearance of greenish precipitate
In Jones Test, Aldehydes are rapidly oxidized to __________?
Carboxylic Acids
What is the reagent for Schiff’s Test?
Schiff’s Reagent
What is the positive result for Schiff’s Test?
appearance of pink or magenta color
It is a test for ketones where the reagent is m-dinitrobenzene
m-dinitrobenzene test
What is the positive result for m-dinitrobenzene test?
appearance of violet color
It is a test for ketones where the reagent is sodium nitroprusside in alkaline medium
Rothera’s Test
What is the positive result for Rothera’s Test?
Appearance of red color complex
It is a polyhydroxy aldehydes or ketones or substances that hydrolyze to yield polyhydroxy aldehydes and ketones
Carbohydrates
What are the classifications of Carbohydrates?
- Monosaccharides
- Disaccharides
- Polysaccharides
It is a reduction test for carbohydrates
Benedict’s Test
It free aldehyde or keto group in the reducing sugars reduce cupric hydroxide in alkaline medium to red colored cuprous oxide
Benedict’s Test
depending on the concentration of sugars, _______________ is developed
yellow to green color
What is the positive result for Benedict’s Test?
Formation of brick red precipitation
All_____________ are reducing sugars as they all have a free reactive carbonyl group.
monosaccharides
TRUE OR FALSE:
Some disaccharides, (i.e. reducing disaccharides) have exposed carbonyl groups but less reactive than monosaccharides.
TRUE
What is the general test for the presence of the carbon-oxygen double bond?
2,4 - DNP Test
2,4,-DNP Test
What are the ways to help identify the specific aldehyde/ketone?
- Recrystallization
- Purification
- MP Determination
MULTIPLE CHOICE:
All of these are the complications of 2,4-DNP Test EXCEPT:
a. Some ketones give oils which will not solidify
b. Some allylic alcohols are oxidized by the reagent to aldehydes and ketones and give positive result
c. Some not pure alcohols may contain aldehyde or ketone impurities
d. The color usually develops in 5-15 secs
d. The color usually develops in 5-15 secs
It is a test for acetaldehyde and methyl ketones where the reagent is I2/NaOH
Iodoform Test for Methyl Ketone
What is the positive result for Iodoform Test for Methyl Ketone?
Formation of a yellow precipitate or suspension of iodoform and a distinct smell
It is the reaction at the alpha carbon where a C-H bond on the alpha carbon to a carbonyl grop is more acidic than many other C-H bonds because reaction with base forms a resonance-stabilized enolate ion
Haloform Reaction
____________ are nucleophiles, and so they react with electrophiles to form new bonds on alpha carbon.
Enolates
Oxidation:
What is formed under alkaline condition?
Salt
TRUE OR FALSE:
When oxidizing, ketones need a stronger oxidzing agent while aldehydes need mild oxidizing agent
TRUE
What are the two complications on Tollen’s Test?
- The tube must be clean and oil free if a silver mirror is to be observed
- Aromatic Amine & some phenols are easily oxidized which give false positive results
What are the complication in Jones Test?
Usually color develops in 5-15 secs
