PHA615 LAB: Classification Tests for Alcohols, Aldehydes, and Ketones

Alcohols (ROH)

is one of the oxygen-containing HC derivative. It

specifically has a hydroxyl- (-OH) functional group on every alcohol

compound.

Alcohols (ROH)

are considered as a weak Brønsted acid with pKa around 15-20.

hydroxyl proton (H+)

is the most electrophilic site and its transfer is

very important to consider in reactions with Nü.

more

Aromatic ROH are _ acidic than aliphatic ROH because of stabilization of the RO- when the H+ leaves the molecule.

Lucas Test

It uses ZnCl2 in HCl to differentiate 1°, 2°, and 3° ROH.

Lucas Test

• It follows a SN1 mechanism and is very reactive with 3° ROH and forms turbid solution with an oily layer immediately.

Jones Oxidation Test

Also known as Chromic acid test.

Jones Oxidation Test

It uses K2Cr2O7 in H2SO4 to form H2Cr2O7 (strong oxidizing agent). Oxidizes 1° ROH and 2° ROH.

Aldehydes (RCOH) and Ketones (RCOR’)

are two classes of carbonyl- containing (C=O) organic compounds. Both are found in nature in combination with other functional groups.

Aldehydes

are commonly found in molecules responsible for different scents or odors.

Ketones

are common in steroidal molecules like hormones.

Aldehydes (RCOH) and Ketones (RCOR’)

exhibits dipole-dipole interaction and weak to no

hydrogen bonding with water.

Aldehydes

can be used as preserving biological species (formaldehyde), manufacture of plastics and resins, and flavorant (benzaldehyde).

Ketones

can be used as solvents, paint remover/thiner (acetone), peeling agent and for acne treatment, and as welding agent (ethyl methyl ketone).

Fehling’s Test

It uses Fehling’s A (made of CuSO4) and Fehling’s B (made of KNaC4H4O6•H2O and NaOH) to differentiate aldehydes from ketones.

Fehling’s A

(made of CuSO4)

Fehling’s B

(made of KNaC4H4O6•H2O and NaOH)

red or brick-red ppt

(positive result) for aldehyde

Tollen’s Silver Mirror Test

Also known as silver mirror test.

Tollen’s Silver Mirror Test

It uses Tollen’s reagent (solution of AgNO3 and NH3) to differentiate aldehydes from ketones.

Tollen’s reagent

(solution of AgNO3 and NH3)

Iodoform Test source

It uses a source of iodine (KI) and a base (NaOCl) to detect the presence of methyl ketones.

Iodoform Test

This test will also test positive with acetaldehyde, ethanol, methyl

ketones, and 2°ROH with methyl group on the alpha carbon.

Branching

weakens the hydrophobic (LDF) force in alcohol making the ROH more polar and water soluble.

3° ROH

will react fastest because of the very stable R+ that it produces.

aldehydes

Only _ will test positive with Fehling’s test.

ɑ-hydrogen

Fehling’s Test follows an oxidation mechanism which will only have a positive result in the presence of an _

Tollen’s Test

is used to confirm the presence of oxidizable carbon found in aldehyde compounds.

aldehydes

Tollen’s Test

Only _ will test positive for this test.

Iodoform Test detects

detects the presence of methyl ketone structure or a methyl carbonyl group.