Organic Chemistry 1 Lab Final Texas A&M Part 1

Volatile organic compounds should

be transferred in the hood

Which chemical was used to destroy excess oxidant in the oxidation of a 2° alcohol experiment?

NaHSO3 - Sodium Bisulfite

A positive bromine test indicates the presence of what?

carbon-carbon double bonds

In the kinetics experiment, two different solvent mixtures were used. One mixture was 50% water-50% ethanol, the other was 60% water-40% ethanol. What would you predict about the rates in the two solvent mixtures?

The rate in the 60% water 40% ethanol mixture would be faster because the solvent better stabilizes the cation.

A phenol (ArOH) that is deprotonated by NaOH will become _______.

ArO- Na+

When hexane was used as the solvent for your Analgesics TLC lab, why didn't the spots move?

Hexane is not able to disrupt the polar-polar interactions between the analgesics and the silica gel

Advantages for the purification of compounds by preparative GC versus distillation

a. You may be able to separate different compounds which have exactly the same boiling point.
b. You can isolate a compound at temperatures well below its boiling point once it has been vaporized.
c. Some compounds which cannot survive the extended heating necessary for distillation may be stable enough to purify by GC.

Gas Chromatography - what happens if you increase the sample volume?

it may decrease resolution

Gas Chromatography - what types of gas can be used as the mobile phase?

An inert gas such as helium or nitrogen

Gas Chromatography - The number of theoretical plates is directly proportional to

column length

Gas Chromatography - smaller particle size produces

a higher number of plates

You have carried out a synthesis and the pot contains your product (a liquid which you plan to distill) and one impurity. You will have to carry out a fractional distillation in order to recover the product in good purity IF THE IMPURITY IS

soluble in the product and volatile

Would NOT be desired in a good recrystallization solvent?

The recrystallization solvent is nonvolatile.

If you have a sample that is known to be either adipic acid or acetanilide, what is a quick way to distinguish the two?

Determine the solubility of each in sodium bicarbonate

Why is it important not to distill a flask/vial to dryness?

the residue in the flask could explode

Which reagent is not an oxidizing agent?

H2O

What is the chemical formula of the precipitate formed in the Baeyer's test? KMnO4

MnO2

What effect on the rate of an SN1 type reaction would there be if you doubled the concentration of the nucleophile?

it would have no effect on the rate

Compounds such as -pinene and (+)-limonene are members of the class of natural products known as:

terpenes

In normal phase thin layer chromatography, the stationary phase is:

polar

What is the volume range of a typical injection for the Preparative Gas Chromatography experiment?

25 - 100 µL

Gas Chromatography: Polar compounds are retained more by

polar columns

To form a salt of an amine, R-NH2, you must add which reagent?

HCl

Infrared spectroscopy may be used to distinguish a primary amine from a secondary amine because:

Primary amines show two absorptions at 3400-3100 cm and secondary amines show only one absorption at 3400-3100 cm.

The computer calculated that the local minimum for the gauche butane conformation had a dihedral angle of:

65 degrees

In the recrystallization of acetanilide, you were asked to allow the hot solution to cool slowly to form crystals. What happens if the solution is cooled rapidly?

small crystals form and adsorb impurities.

Which of the following functional groups has sp hybridization?

Alkyne

The distillate collected whilst dehydrating cyclohexanol is an azeotropic mixture of cyclohexene and water. What is the composition ratio of cyclohexene to water?

90:10

In the solvolysis reaction of 1-chloro-1-phenylethane what is the nucleophile?

water

In the phase transfer catalysis experiment, the role of benzyltri-n-butylammonium chloride is

to carry the naphtholate anion to the organic phase.

Steam distillation is useful for isolating compounds that:

are water immiscible with low vapor pressure at room temperature

Thin Layer Chromatography (TLC)

The solvent moves through the stationary phase by capillary action.

Which of the following does NOT influence the separation of a mixture of compounds in gas chromatography?

the densities of the compounds in the sample

In simple distillation, the temperature frequently drops after the main fractions have distilled because:

not enough vapor and condensate are present in the head to keep the thermometer bulb hot

To separate two compounds by liquid-liquid extraction, the compounds must

be distributed unevenly between the two immiscible liquids.

Which of the following is the most polar compound?
a. acetone b. acetic acid c. water d. toluene e. cyclohexane

water

Based on VSEPR theory, what is the hybridization of the nitrogen atom and the approximate bond angles around nitrogen in methylamine, CH3NH2?

sp3 and 109.5 degrees

The mini-column used in the phase transfer catalysis contains

silica gel like the particles on the TLC plate, only larger in particle size

The mini-column used in the phase transfer - which product elutes out first?

naphthyl ether

In TLC, a Rf value is

the ratio of the distance the compound moved divided by the distance the solvent moved

In gas chromatography, the efficiency of separation does NOT depend on the:

type of detector used

In a distillation, one vaporization and condensation step is usually called a

Theoretical plate

A mixture of benzoic acid, benzyl chloride and cyclohexyl amine is dissolved in dichloromethane. The solution is extracted with dilute aqueous HCl and the layers separated. The dichloromethane layer contains: 1. cyclohexyl amine 2. benzoic acid 3. benzyl chloride

2 and 3

Which of the following statements is FALSE for recrystallization as a method for purification of organic compounds?
a. Low solubility of the compound at low temperatures minimizes the amount of the purified compound that will be lost during recrystallization.
b. If the impurities are soluble, they may be removed by filtration at high temperatures.
c. Scratching the side of the beaker with a stirring rod may induce crystallization.
d. Recrystallization is often used to purify solids.
e. A good recrystallization solvent should be reasonably volatile.

b

In the Who Has My Compound experiment, which technique did you not use to determine your compound?

boiling point determination

GC - the typical column of a GC is constructed of a

long, coiled tube

GC - the column is contained in an

oven

GC - longer columns give better

resolution or separation

GC - column contains an

inert, powdered solid

Which of the following would not be a role of the phase transfer catalyst?
a. increases the yield of the desired product
b. changes the solubility of the reactant ion
c. allows both of the reactants to be solvated in the organic solvent
d. aids in the separation of the products of the reaction
e. promotes the reaction by pairing the hydrophillic ion with a hydrophobic counter ion

d