CA2

Handling volatile solvents

True: Volatile solvents must be used only in well-ventilated areas such as a fume hood to limit inhalation exposure

characteristics of an organic extracting solvent

can't mix with water and dissolve various organic compounds

Flammability of organic solvents

True: Many organic solvents are flammable and must be kept away from ignition sources

Pressure buildup in separatory funnels

True: Volatile solvents can cause pressure buildup and must be periodically vented during extraction

Use of PPE in wet labs

True: Appropriate gloves must be worn when handling all chemical reagents

Disposal of organic waste

True: Organic solvents must be disposed of only in designated labeled waste containers

Purpose of drying agents in extraction

To remove residual water from the organic layer after separation

Good separating solvent must

dissolve the solute better than initial solvent and unmixable with water

Why drying agents are added at the end of extraction

To ensure the organic phase is anhydrous before evaporation or further purification

Density ranking in biphasic extraction

The denser solvent forms the bottom layer during liquid-liquid extraction

Layer identity in Ether/Water extractions

The ether layer is typically the top layer because ether has lower density than water

Layer identity in DCM/Water extractions

Dichloromethane forms the bottom layer because it is denser than water

Proper filling volume of separatory funnel

False: The separatory funnel should not be filled completely to avoid dangerous pressure buildup

Importance of venting during shaking

True: Venting prevents pressure accumulation and allows safer mixing

Direction of the stopcock during venting

True: The tip must be pointed away from all personnel while venting vapors

Shaking intensity for separatory funnel

False: Excessive shaking increases risk of leaks or emulsion formation

Calculation of percent recovery

Percent recovery = (mass recovered / initial mass) × 100

Purpose of mass recovery in extraction

To evaluate the efficiency of isolating each target component

Molecule with zero net dipole in linear geometry

Carbon dioxide ↹

Cause of differences in Rf values in TLC

All factors such as solvent choice, adsorbent, and amount spotted affect Rf ↹

Purpose of TLC

check purity of compounds and monitor reactions

Rf calculation formula

Distance traveled by compound divided by distance traveled by solvent front ↹

Visualization of TLC spots in many labs

Ultraviolet light is commonly used to visualize compounds that absorb UV ↹

Why polar compounds show lower Rf

Stronger interactions with polar stationary phase reduce travel distance ↹

Role of developing chamber saturation

Ensures consistent solvent vapor environment for reproducible Rf values ↹

Appropriate spotting technique in TLC

Apply very small concentrated spots to avoid streaking and mixing ↹

Reason CO2 is nonpolar despite polar bonds

Symmetrical linear structure results in canceling dipoles ↹

Chromatography separation principle

Differential affinity between stationary and mobile phases determines compound migration ↹

Preference of simple distillation

To achieve a single vaporization-condensation cycle for separating components with large boiling point differences

Purpose of fractional distillation

To allow repeated vaporization-condensation cycles by using a fractionating column

Reason fractional distillation is more efficient

Greater number of theoretical plates increases separation efficiency

Gas chromatography utility

Used to separate mixture components and determine identity and relative abundance

Retention time in non-polar GC column

Lower boiling point compounds elute faster and show shorter retention times

Interpreting GC peak area

It quantifies the relative amount of a given compound in the mixture

Boiling point and GC retention relationship

Higher boiling point compounds remain in the stationary phase longer (harder to evaporate)

Safety consideration in distillation

Ensure cooling water circulates properly through condenser to manage vapor condensation

Sign of good TLC/GC separation

Distinct non-overlapping peaks or spots indicate effective component resolution

Purpose of theoretical plates in fractional distillation

increase separation through multiple cycles of vaporization and condensation

Extraction techniques

liquid-liquid and solid-liquid

Liquid-liquid extraction

Solute distributes between an organic solvent and water to achieve separation

Solid-liquid extraction

Solid components are transferred into a liquid solvent such as water or organic solvent

Kd greater than 1

Solute is more soluble in the extracting solvent (S2) than the original solvent (S1)

Kd less than 1

Solute remains more soluble in the original solvent (S1)

Requirements of a good extracting solvent

Must be immiscible with water, dissolve organic compounds, be unreactive, and have low boiling point

Separatory funnel technique

Vent frequently to relieve pressure and separate layers correctly

Draining lower layer in separatory funnel

Drain through the stopcock into a container

Removing upper layer in separatory funnel

Pour out the top of the funnel into a labeled container

Acid-base extraction principle

selective partioning of components between an organic solvent and water

Example acid in ether vs water

Acid is soluble in ether but can form water-soluble salts when deprotonated

Example base in ether vs water

Base is soluble in ether but can form water-soluble salts when protonated

Converting salts back to neutral compounds

Add strong acid to protonate bases or strong base to deprotonate acids

Organic acid behavior in extraction

Forms a carboxylate salt in basic aqueous layer and later re-precipitates with strong acid addition

Organic base behavior in extraction

Forms a protonated salt in acidic aqueous layer and later re-precipitates with strong base addition

Organic neutral compound behavior

Remains in the organic layer throughout extraction

Techniques used in this experiment

Vacuum filtration, separatory funnel extraction, Digimelt melting point measurement

Goal of this experiment

Separate and identify each component of a trinary mixture then calculate percent recovery

Partition coefficient (Kd)

solubility of a solute in two different solutions

Kd equation

grams A extracted in S2/ grams A remaining in S1

Good extracting solvent

Should be immiscible with water, dissolve a wide range of organics, be unreactive, and have a low boiling point for easy removal.

Separatory funnel

Vessel used for liquid-liquid extraction; lower layer is drained through stem, upper layer is poured out

separatory funnel safety considerations

must be vented regularly to release pressure.

Acid-base extraction

Separation method where an acid or base reacts to form a water-soluble salt that partitions into the aqueous layer.

Conversion of salts back to neutral compounds

Acidic salts are neutralized with strong acid; basic salts are neutralized with strong base to regenerate the parent acid or base.

Trinary mixture separation

Involves separating an organic acid, base, and neutral compound using acid-base extractions and solvents like DCM, HCl, NaOH, and NaHCO3.

acid-base extraction phases

aqueous and organic

acid-base extractions occur during

dissolution, chemical conversion to a salt, separation into aqueous and organic phases

Thin-layer chromatography (TLC)

Liquid-solid chromatography technique using a solid stationary phase and a liquid mobile phase to separate compounds by polarity.

Stationary phase (TLC)

Solid adsorbent like silica or alumina coated on a plate.

Mobile phase (TLC)

Liquid solvent or solvent mixture that moves through the stationary phase carrying compounds.

Retention factor (Rf)

Ratio of the distance a compound travels to the distance the solvent front travels; Rf = distance solute / distance solvent.

Polarity and Rf relationship

More polar compounds interact more with the stationary phase (adsorbent) and move less/slower (lower Rf).

Visualization methods (TLC)

Techniques like UV light, iodine, permanganate, phosphomolybdic acid, and 2,4-DNP used to visualize spots on TLC plates.

Non-destructive visualization

Methods such as UV light that do not alter compounds on the TLC plate.

Destructive visualization

Methods involving chemical reactions between reagents and components (e.g., PMA, iodine vapor).

Applications of TLC

Used to check purity, identify compounds, monitor reactions, and separate mixtures on a small scale.

Distillation

Process of separating liquid mixture components by selective boiling and condensation based on different boiling points.

Distilland

The liquid mixture being heated during distillation.

Distillate

The vapor that condenses and is collected during distillation.

two types of distillates collected in fractional distillation

lower boiling point component and residue

HETP

height equivalent to a theoretical plate, column efficiency

Simple distillation

Single vaporization-condensation cycle used to separate components with large boiling point differences (>100°C).

Fractional distillation

Involves multiple vaporization-condensation cycles using a fractionating column to separate liquids with small boiling point differences.

Theoretical plate

Represents one vaporization-condensation cycle; more plates mean better separation efficiency.

HETP (Height Equivalent to a Theoretical Plate)

Column height divided by number of theoretical plates; lower HETP means higher efficiency.

Gas chromatography (GC)

analyzing and separating volatile components (liquid) based on partitioning between a gas mobile phase and liquid stationary phase.

Purpose of column in gc

enable division between gas and liquid phases

Mobile phase (GC)

Inert carrier gas such as helium, nitrogen, or argon.

Role of the carrier gas in gas chromatography

it transports vaporized components through the column

Stationary phase (GC)

Non-volatile liquid coated on a solid support inside the column.

Retention time (tR)

Time it takes a component to travel through the GC column to the detector; used to identify compounds.

factors that influence retention time

boiling point, polarity, flow rate, column temp

Chromatogram

Graphical output of GC showing peaks corresponding to components of a mixture.

Peak area (GC)

Proportional to the amount of each component in a mixture; used to calculate percent composition.

% composition formula (GC)

% Component X = (Area of X / Total Area) × 100%.

Factors affecting retention time (GC)

Boiling point, stationary phase polarity, carrier gas flow rate, column temperature, and column length.

Simple vs. fractional distillation

Simple distillation involves one vaporization-condensation; fractional uses multiple cycles via a packed column

Column efficiency in distillation

Measured by HETP; a lower value means the column achieves more effective separations per unit height.

Efficiency in distillation measured by

analyzing boiling temperatures

Polarity and chromatography

More polar compounds adsorb more strongly to polar stationary phases (e.g., silica), reducing mobility.

Molecular polarity

Measured by dipole moment; influences solubility, interactions, and chromatographic behavior.