3-Step Synthesis

Question 1

In step one (Benzaldehyde to Benzoin), what is the molar mass of benzaldehyde (C6H5CHO)?

Answer 1

106.12 g/mol

Question 2

What is the purpose of crushing the vitamin B 1 tablets?

Answer 2

An increase of surface area allows for more points of attack for the solvent.

Question 3

What is the purpose of ethanol in step one (benzaldehyde to benzoin)

Answer 3

ethanol creates an organic environment for the reaction to occur.

Question 4

What is the purpose of sodium hydroxide in step one?

Question 5

Why must the water bath in step 1 not exceed 60-65 degrees?

Answer 5

Thiamine is heat sensitive and will decompose if heated too much.

Question 6

What type of reaction is step 1 (benzaldehyde to benzoin)?

Answer 6

Condensation (two molecules become condense to one molecule).

Question 7

Why does the temperature of the solution need to be below 20 degrees when sodium hydroxide is added in step 1?

Answer 7

Makes reaction a little bit slower to allow for more product to form. Cooling the sodium hydroxide lowers the rate of the reaction with thiamine

Question 8

Why does the solution change color to yellow in step 1?

Answer 8

the reaction between sodium hydroxide and thiamine is complete.

Question 9

why should the flask be covered with parafilm in step 1 before heating for 2 hours?

Answer 9

parafilm allows for minimal escape of gases and bubbling over.

Question 10

What is the purpose of the last ice bath in step 1?

Answer 10

the ice bath encourages precipitation of the product

Question 11

Why is hot ethanol used as the solvent in recrystalization?

Answer 11

Hot ethanol will dissolve the product, but not impurities. Impurities will be filtered out and the product will be in the bottom in liquid form.

Question 12

Why does step 2 need to be performed in the fume hood?

Answer 12

The reaction of benzoin to benzil proceeds with the formation of NO2 gas, which is toxic.

Question 13

what is the purpose of concentrated nitric acid in step 2?

Answer 13

Nitric acid acts as a catalyst.

Question 14

What is the limiting reagent in step 2?

Answer 14

Benzoin

Question 15

what is the molar mass of benzoin (C14H12O2)?

Answer 15

212.25 g/mol

Question 16

Why shouldn’t the reaction temperature in step 2 not exceed 70 degrees?

Answer 16

nitric acid is heat sensitive and boils at 84 degrees.

Question 17

What is the molar mass of benzil?

Answer 17

210.23 g/mol

Question 18

what is the purpose of potassium hydroxide in step 3 of the experiment?

Answer 18

potassium hydroxide provides the hydroxyl group needed to attack the carbonyl carbon, resulting in an electronegative oxygen ion.

Question 19

What is the purpose of the hot water in the third step?

Answer 19

Allows for the establishment of proper reaction conditions for when the HCl is added.

Question 20

Why do we add HCl in step 3?

Answer 20

provides necessary hydrogen to convert the oxygen ion to a hydroxide, completing the formation of the carboxylic acid

Question 21

What impurity does the cold water in step 3 remove from benzilic acid?

Answer 21

salts

Question 22

What are the safety hazards of step 1 (Benzaldehyde to Benzoin)

Answer 22

Sodium hydroxide (NaOH) is corrosive to skin, eyes and clothing.
Ethanol and benzaldehyde are volatile and create fumes

Question 23

What are the safety hazards in step 2 (Benzoin to Benzil)?

Answer 23

Nitric acid is corrosive and destructive to skin, eyes, and clothing. It also creates dangerous fumes.

Question 24

What are the safety hazards in step 3 (benzil to Benzoic Acid)?

Answer 24

Potassium Hydroxide is corrosive and destructive to skin, eyes, and clothing. Hydrochloric acid should also be used with caution.

Question 25

What is the molar mass of benzilic acid?

Answer 25

228.24 g/mol

Question 26

Answer 26

Benzaldehyde

Question 27

Answer 27

Benzoin

Question 28

Answer 28

Benzil

Question 29

Answer 29

Benzilic Acid