Orgo Lab Exam 1

matter

Any substance that is made up of small tiny particles “atoms”, occupies space, and has a mass is called matter

Physical Properties of matter

Characteristics of matter that can be observed \n without changing its nature or reacting with \n other substances. \n

Ex: volume, mass, boiling point, melting point, \n density...

Chemical Properties of matter

Characteristics of matter that can be observed and determined only during chemical changes.

Ex: reactivity, flammability, toxicity, stability.

extensive vs intensive properties

Physical Properties of Matter

extensive properties

These properties depend on the amount of the substance such as the mass, volume

Intensive Properties

These properties don’t depend on the amount of the substance such as boiling point, melting point, density, conductivity

Intramolecular Forces

These forces exist between the elements within the same compound and help them to stay intact. These forces mainly determine the **chemical properties** of a substance

Intermolecular Forces

These forces exist between separate molecules of a certain substance. These forces mainly determine the **intensive physical properties** of a substance

Intermolecular forces are ____ than intramolecular ones

weaker

Intermolecular Forces are measured using

melting and boiling points

Dipole-Dipole Interactions (Keesom Forces)

strongest

Induced Dipole-Dipole Interactions (Debye Forces)

They exist between non-polar molecules (Induced dipole) and polar ones (Dipole)

Strength of induced-dipole-dipole interactions depends on the

• Polarity of the polar molecule.

• Polarizability of the non-polar one

Induced Dipole-Induced Dipole Interactions (London-Dispersion Forces)

• They exist in all molecules polar and nonpolar

• They are important only in nonpolar molecules.

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Strength of induced-dipole-induced dipole interactions

As surface area of the compound increases, their strength increases

Solubility

Is the maximum amount of solute that can be completely dissolved in a certain amount of solvent at a certain temperature

Factors Affecting Solubility

• Properties of Solute & Solvent

• Temperature

Recrystallization

Is a purification technique that is mainly used to purify solids

Recrystallization principle

• Different solutes have different solubilities in the same solvent.

• Solubility decreases as temperature decreases.

• Molecules of the same compound have higher tendency to stick together (crystallize together)

choosing solvent for recrystallization

Solvent should be a poor solvent at room temperature and good at high temperature

Extraction

a purification /separation technique that can be used to separate compounds based on their partition between two media (one compound has more affinity toward one media than the other

Extraction principle

Compounds have different solubilities in different solvents

Usually aqueous layer is the bottom one except for halogenated organic solvents like DCM. Why??

DCM has a higher density than water

Multiple extractions with smaller volumes are more efficient.

3 extractions with 20 mL is better than 1 extraction with 60 mL

K equation

To move organic acids like carbolic acid to the aqueous layer,

add a base like NaOH

To move organic bases like RNH2 to the aqueous layer,

add an acid

Chromatography

Chromatography is the separation of a mixture of two or more compounds into its constituents

Stationary phase

Interacts with the mixture and causes separation

Mobile phase

Push the mixture to move over the stationary phase

Chromatography Principle

• Different compounds interact in different ways with the stationary phase.

• Strongly interacting ones will be delayed.

• Weakly interacting ones will move quickly

Why do why have a mix of polar and nonpolar solvents in chromatography ?

addition of only a minor amount of a polar solvent can result in a large increase in the eluting power of the mixture

Thin Layer Chromatography Uses

• To purify small amounts of compounds (rare)

• Qualitative test for purity of mixtures.

• Identify number of compounds in a mixture

• To identify unknowns.

• To monitor separation in column chromatography (CC)

• To find the best solvent for CC

Explain the correlation between Retardation Factor and polarity

Rf = Dspot / D solvent

The more polar a compound is, the smaller the Rf value

melting point

Temperature at which the solid and liquid phases of a pure substance coexist at 1 atm

Increase in atmospheric pressure, (Blank) the m.p.

increases

Compounds with Crystal lattice structure have a (blank) m.p

higher

What does impurities do to the melting point

Impurities reduce the m.p. and increase the range of melting

Boiling Point

Temperature at which the vapor pressure of a liquid equals the atmospheric pressure

As the strength of intermolecular forces increases, vapor pressure (blank)

decreases

As vapor pressure increases, b.p. (blank)

decreases

As atmospheric pressure decreases, boiling point (blank)

decreases

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Vapor pressure will equalize the atmospheric temperature at a lower temperature

Distillation

Is a separation/purification technique that can be used to purify volatile liquids based on the difference between their boiling points

Fractional Distillation

• Separate liquids with very close boiling points.

• Use a fractionating column Mixture: Consists of a mixture of (A, b.p. = 100 °C) & (B, b.p. =75 °C )

• Upon heating, vapor goes up, consists of A & B

• “A” has higher b.p. so it starts to condense

• As we move up the column, the vapor fractions will consist more of “B”

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Vacuum Distillation

• Distillation under vacuum (reduced pressure)

• The reduced pressure lowers the boiling point.

• This makes the distillation faster.

Steam Distillation

• Mixing of organic solvent and water (immiscible).

• The organic solvent will distill at a low temperature.

• Each solvent exerts its own pressure

• The total pressure will get closer to the atmospheric pressure faster.

Qualitative Tests

It uses chemical tests “visual” to confirm the presence or absence of a certain functional group

Jones Oxidation

• The oxidizing agent is **CrO3, H2SO4**

• 1’ alcohol to carboxylic acid

• 2’ alcohol to ketone

• aldehydes to carboxylic acid

• Color changes from orange “Cr(III) to green to blue color Cr(IV)

Lucas Test

• It is used to differentiate between primary, secondary & tertiary alcohols

• The reagents used are **HCl with ZnCl2**

• Converts alcohols into alkyl halides

• Primary alcohols doesn’t react unless it is heated

• Secondary alcohol turns turbid and forms an oily layer in three to five minutes

• tertiary alcohols react rapidly and give turbid solution with oily layer

Ferric Chloride Test

• **FeCl3** is used to test for phenols.

• Phenol forms red-blue-violet complex with Fe(III)

Derivative Test

• Convert aldehydes and ketones into other derivatives.

• 2,4-dinitrophenylhydrazine & semicarbazone

• They convert liquid aldehydes and ketones into solids

Tollen’s Test

• It is used to test for aldehydes

• The reagents used are **AgNO3 and HO-**

• The aldehyde is oxidized to carboxylic acid.

• Ag(I) is reduced to Ag (silver mirror)

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Iodoform Test

• Test for presence of methyl ketones

• Reagents used are iodine **I2 and -OH**

• It gives a carboxylate and Iodoform (HCl3) (yellow precipitate)

Bromine Test

• Test for presence of double or triple bonds

• Reagent used is bromine **Br2** (red color)

• Bromine adds to the double bond or triple bonds and since it is consumed the red color disappears

Permanganate Test

• Test for presence of double or triple bonds

• Reagents used are **KMnO4 & HO-** (purple color)

• It adds two hydroxyl groups to the double bond

• Since the permanganate is consumed the color disappears

In distillation, the cold water should enter from the top side of the condenser (T/F)

False

Which will have a lower Rf value, chlorobenzene or phenol?

phenol

rotary evaporator

The reduced pressure in the apparatus causes the solvent to boil at a lower temperature than normal (see vacuum distillation), and rotating the flask increases the liquid's surface area and thus the rate of evaporation

the most polar compound will be

the one with the oxygen

steam distillation use is to

purify volatile liquid(s)

Which solvent mixture is better to separate B & C? Explain briefly (2 points)

I: Hexane: Ethyl acetate (5:3)

II: Hexane: Ethyl acetate (5:1)

II: Hexane: Ethyl acetate (5:1)

We need a less polar solvent