orgo 1 +2 lab final pt.2

Which of the following best describes silica gel stationary phase?

extremely polar

extremely nonpolar

slightly nonpolar

slightly polar

Extremely polar

the distance a solute travels on the stationary phase depends mainly on what molecular characteristics?

Shape

Polarity

Purity

Size

Polarity

What is the correct ranking of these samples in order of increasing polarity (from least polar to most polar)

C < B < A

B < C < A

C < A < B

B < A < C

B<A<C

T/F: When spotting a sample onto the TLC plate, the size of the spot should be as large as possible

F

Which of the following methods can be used to detect the solute spots on the tlc Plate?

1.Putting the plate under a UV lamp
2. Exposing the plate to a developing stain
3. Feeling the spots on the plate with fingertips

1, 2

Rf calculation for the spot shown, what is rf =

distance A,B,C,D

divide, minus, plus, multiply

distance A,B,C,D

D/B

Which of the following statements is false?

An extremely polar substance can have an R_f value of 0.

Less-polar substances travel farther than more polar substances.

Some extremely nonpolar substances may have R_f values above 1

The more polar a substance, the lower is its R_f value.

some extremely nonpolar substance may have Rf values above 1

Examine the structures of biphenyl, benzil, and benzoin given in the procedure and pre-lab lecture. Which is most polar?

benzil

biphenyl

benzoin

all have the same polarity

Benzoin

The solvent systems in this experiment will be mixtures of ethyl acetate and hexanes. Which one is Less polar?

ethyl acetate 

hexanes

Hexanes

The following silica-gel TLC plate was developed with a 20:80 solvent system (20% ethyl acetate and 80% hexanes). How should the solvent system be changed to allow the components to travel farther up the plate?

make the solvent more polar by increasing the amount of ethyl acetate (30:70)

make the solvent less polar by increasing the amount of hexanes (10:90)

make the solvent more polar by increasing the amount of ethyl acetate (30:70)

Which statement correctly describes the mechanism of the following reaction?

the nucleophilic carbonyl carbon attacks the electrophilic hydride reagent

the nucleophilic hydride reagent attacks the electrophilic carbonyl carbon 

the electrophilic carbonyl carbon attacks the nucleophilic hydride reagent

the electrophilic hydride reagent attacks the nucleophilic carbonyl carbon

the nucleophilic hydride reagent attacks the electrophilic carbonyl carbon

The reaction flask needs to be cooled before adding sodium borohydride because the resulting reaction is highly blank

exothermic

T/F: A properly made ice bath contains both solid ice and liquid water

T

According to the sds, which of the following is/are potential hazards of sodium borohydride?

reacts violently with water

toxic if swallowed

causes severe skin burns and eye damage

reacts violently with water

toxic if swallowed

causes severe skin burns and eye damages

T/F: the sodium borohydride should be weighted at the very beginning of lab and left on the bench top until it is added to the reaction?

F

Considered the structures of the reactant and product. Where should the spots appear on a TLC plate relative to each other?

The reactant and product will have approximately the same Rf values.

The reactant will have a smaller Rf value then that of the product.

The reactant will have a larger Rf value than that of the product.

The reactant will have two spots, while the product will show three spots.

The reactant will have a larger Rf values than that of the product

What solvent system will be used for TLC analysis?

75 % ethyl acetate: 25 % hexanes

10 % ethyl acetate: 90 % hexanes

50 % ethyl acetate: 50 % hexanes 

25 % ethyl acetate: 75 % hexanes

25% ethyl acetate, 75% Hexanes

T/F: Once TLC analysis shows the reaction is complete, the solution will be quenched with a mixture of 3M hydrochloric acid and ice

T

How will the diphenylmethanol product be isolated?

TLC 

IR spectroscopy

vacuum filtration

simple distillation

vacuum filtration

What change in the IR spectrum would suggest that benzophenone has been converted to diphenylmethanol?

The disappearance of a sharp peak around 1700 cm^-1 and the appearance of a broad peak around 3300 cm^-1.

The appearance of a sharp peak at 3100 cm^-1 only.

The disappearance of a sharp peak around 1700 cm^-1 only.

The disappearance of a sharp peak around 3400 cm^-1 and the appearance of a broad peak around 1700 cm^-1.

the disappearance of a sharp peak around 1700cm and the appearance of a broad peak around 3300cm.

What functional groups react in a fischer esterification reactions?

ester 

alcohol 

carboxylic acid

acid chloride

alcohol and carboxylic acid

which reactant provides the arrow-indicated oxygen in isopentyl acetate?

acetic acid

phosphoric acid

water

isopentyl alcohol

isopentyl alcohol

Which technique will achieve the long-term heating necessary for this reaction?

simple distillation

vacuum filtration

recrystallization

reflux

reflux

Which of the following remains constant during reflux? Choose apply

moles of reactant

volume of solvent

grams of product

temperature of reaction

volume of solvent and temperature of reaction

What is the procedure for isopentyl acetate reaction?

First, second, third, fourth

secure reaction mixture by clamping round bottom flask neck

collect ir spectra

separate the reaction

heat reaction mixture to refluc

first- secure reaction mixture by clamping round bottom flask neck

second - heat reaction mixture to reflux

third- separate the reaction mixture with DI water

fourth- collect ir spectra

which of the following is the catalyst that will be used in this lab isopentyl acetate experiment?

water

isopentyl alcohol

acetic acid

phosphoric acid

phosphoric acid

Starting with 1.5 mL of isopentyl alcohol, 2.0 mL of concentrated acetic acid, and 0.4 mL of concentrated phosphoric acid, what is the theoretical yield (in g) of isopentyl acetate? Necessary values are given below:

1.794

what is the primary hazard to consider when using concentrated acid

flammable 

radioactive

explosive

corrosive

corrosive

which of the following explains why 4-aminophenol is acetylated at the amine group rather than the phenol group?

the nitrogen is more electronegative than the oxygen

the nitrogen is less sterically hindered than the oxygen 

the nitrogen is smaller than the oxygen

the nitrogen is less electronegative than the oxygen

the nitrogen is less electronegative than the oxygen

Starting with 3.00 g of 4-aminophenol (109.13 g/mol) and excess acetic anhydride (102.09 g/mol), what is the theoretical yield (in g) of acetaminophen (151.16 g/mol)?

4.16

which of the following measurement will be used to calculate the percent yield for the reaction acetaminophen?

mass of 4-aminophenol

mass of recrystallized product

mass of crude product

 volume of acetic anhydride

mass of 4-aminophenol and mass of recrystallized product

T/F: the purpose of cooling the reaction mixture (steps 5-7) is to avoid heat build-up from the exothermic reaction

F

What solvent system will be used for recrystallizing the crude product?

ethyl acetate and ammonium hydroxide

50% aqueous methanol

100% water

100% acetone

50% aqueous methanol

What is the approximate volume of solvent recommended per 1 g of crude product?

6 mL

4 mL

3 mL

1.5 mL

3ml

What solvent system will be used to develop the TLC plate?

ethyl acetate and ammonium hydroxide 

100% acetone

100% water

50% aqueous methanol

ethyl acetate and ammonium hydroxide

According to the SDS, which of the following is/are potential hazards of ammonium hydroxide?

Aquatic toxicity

Serious eye damage

Skin corrosion

Oral and/or respiratory acute toxicity

auqatic toxicity, serous eye damage, skin corrosion, oral and or respiratory acute toxicity

which of the following date will you use to compare the crude product vs the recrystallized product

IR spectra

TLC

Melting point

Recrystallization

ir spectra maybe melting point