Organic Chemistry Functional Group Identification Tests

Comprehensive practice flashcards covering qualitative analysis tests for various functional groups including alkenes, carbohydrates, proteins, amines, aldehydes, ketones, phenols, and alcohols.

What is the observation for Alkenes or Alkynes when the Bromine Water Test is performed?

The disappearance of the REDDISH-BROWN color.

What are the reagents used for Baeyer's Test and what is the positive observation?

The reagent is cold dil. $KMnO_4$. The observation is the PINK color turning colorless, forming a brown precipitate of $MnO_2$.

Which types of alkynes give a REDDISH-BROWN precipitate with Ammoniacal $CuCl$?

Terminal Alkynes ($T. ALKYNES$); internal alkynes do not give this test.

What is the observation for Terminal Alkynes when treated with Tollens' reagent ($Ag(NH_3)_2^+$)?

A WHITE precipitate is formed.

What indicates a positive Molisch's Test for Carbohydrates?

A PURPLE / VIOLET ring forms at the junction of the two liquid layers using 1% naphthol in ethanol and conc. $H_2SO_4$.

Which carbohydrates give a negative result for the Tollens' Test (Silver Mirror Test)?

Sucrose and polysaccharides.

How does Barfoed's Test distinguish between Monosaccharides and Disaccharides?

Monosaccharides form a RED precipitate of $Cu_2O$ within 2–3 minutes, while disaccharides react very slowly (10+ minutes).

What is the specific reagent and observation for Seliwanoff’s Test?

The reagent is Resorcinol in dilute $HCl$. The observation is the development of a CHERRY RED / dark red color within 1–2 minutes on heating for Ketoses.

What is the common observation for Fehling's test in the presence of Carbohydrates?

The solution yields a brick-RED precipitate.

What color develops during a positive Biuret test for proteins?

A VIOLET / PURPLE color develops using alkaline copper sulfate.

What color is produced by Proline in the Ninhydrin test?

Proline yields a yellow color rather than the standard Ruhemann's PURPLE.

Which amino acids are specifically identified by the Xanthoproteic Test?

Tyrosine, Tryptophan, and Phenylalanine (proteins with an aromatic ring).

The Sakaguchi Test is specific for which amino acid and why?

It is specific for Arginine due to the presence of the guanidino group, yielding an intense REDDISH-PINK color.

Describe the results of the Hinsberg test for $1^{\circ}$, $2^{\circ}$, and $3^{\circ}$ amines.

$1^{\circ}$ amine: first white ppt. which dissolves in NaOH; $2^{\circ}$ amine: first white ppt. insoluble in NaOH; $3^{\circ}$ amine: No ppt at all.

What is observed when a $2^{\circ}$ amine reacts with Nitrous acid ($NaNO_2 + \text{dil. } HCl$)?

The formation of a yellow oil ($R_2N-N=O$).

What functional group is identified by the Carbylamine test and what is the characteristic result?

It identifies $1^{\circ}$ amines (aliphatic & aromatic) by the FOUL / extremely offensive SMELL of Isocyanide.

Which test results in a YELLOW-ORANGE precipitate for both aldehydes and ketones?

2,4-DNP test (or BRADY test) using 2,4-dinitro phenyl hydrazine.

Does Fehling’s test work for Aromatic aldehydes?

No, Aromatic aldehydes do NOT give this test.

What is the result of the Iodoform Test and what substance is formed?

A YELLOW precipitate of $CHI_3$ is formed.

What is the observation for Phenols in the Ferric chloride test?

VIOLET coloration due to the formation of a complex like $[Fe(OC_6H_5)_6]^{3-}$.

What color changes occur in Liebermann’s test for phenols?

The aqueous solution is RED, then turns BLUE/GREEN upon adding excess NaOH solution.

What are the results for the Victor Meyer test for $1^{\circ}$, $2^{\circ}$, and $3^{\circ}$ alcohols?

$1^{\circ}$ alcohol: Red color; $2^{\circ}$ alcohol: Blue color; $3^{\circ}$ alcohol: No color.

How do different alcohols react in the Lucas test ($conc. HCl + \text{anhyd. } ZnCl_2$)?

$3^{\circ}$ alc: immediate turbidity; $2^{\circ}$ alc: turbidity in 5–8 mins; $1^{\circ}$ alc: No turbidity.

What is the observation for the bicarbonate test for Carboxylic acids?

$CO_2$ gas liberation (effervescence) upon adding $NaHCO_3$.

What is the result of the Mulliken-Barker Test for the Nitro group?

The formation of a Black precipitate or Silver mirror after reaction with $Zn/NH_4Cl$ followed by Tollens' reagent.