Activity No. 10

Question 1

one of the fundamental reactions of organic chemistry and is used extensively in organic synthesis

Answer 1

aldol condensation

Question 2

this reaction is wide in scope and may be used ro condense various combinations of aldehydes and ketones leading to the formation of new carbon-carbon bonds

Answer 2

aldol condensation

Question 3

the mixed condensation of an aldehyde having no a-hydrogen atom w/ a ketone

Answer 3

Claisen-Schmidt reaction

Question 4

this variation of the aldol condensation is illustrated by the synthesis of

Answer 4

dibenzalacetone

Question 5

the reaction conditions of this experiment favor the formation of

Answer 5

dibenzalacetone

Question 6

the product that is insoluble in the aqueous alcohol solvent and precipitates from the reaction as it is formed

Answer 6

dibenzalacetone

Question 7

the starting materials and intermediate which are soluble in aqueous alcohol

Answer 7

benzalacetone

Question 8

the aldol reaction involves the addition of a ___________ or ________________

Answer 8

(a) deprotonated a-carbon atom of an aldehyde
(b) ketone to a carbonyl carbon of an aldehyde or ketone

Question 9

the reaction is generally __________ and involves several mechanistic steps

Answer 9

base catalyzed

Question 10

what will be conducted for the characterization of the product

Answer 10

a preliminary ignition test

Question 11

ignition test should indicate that the product contains _______

Answer 11

an aromatic ring system

Question 12

several classification tests might also be of assistance in classifying the product. What are these? (2)

Answer 12

(1) 2,4-dinitrophenylhydrazine test
(2) Baeyer’s test

Question 13

this alternative test is conducted to indicate the presence of the carbonyl as a ketone

Answer 13

2,4-dintrophenylhydrazine test

Question 14

this another alternative test,baeyer’s test, is conducted for

Answer 14

the presence of unsaturation

Question 15

step 1 in the procedure

Answer 15

In a 50 mil Erlenmeyer flask containing a spinning bar, place 8 ml of benzaldehyde and 3ml acetone

Question 16

how do to prevent loss of acetone by evaporation?

Answer 16

cool the flask, fitted w/ the glass-tube fitted cork, in an ice bath and add the acetone by volume using syringe

Question 17

Step 2 of the procedure (act #10)

Answer 17

to the reaction mixture, add 20 ml of the NaOH catalyst solution. Stir the reaction mixture at room temp. (30 min). During this time, a YELLOW SOLID PRODUCT PRECIPITATES FROM THE SOLUTION

Question 18

Step 3 of the procedure (activity #10)

Answer 18

remove the spinning bar, collect the crude yellow dibenzalacetone by FILTRATION. transfer the collected filter cake to a 50mL beaker, stir with 25ml of water.

Question 19

step 4 of the procedure

Answer 19

give time for the product to settle at the bottom of the beaker and then remove the aqeuous layer by DECANTATION. repeat the process (about 3 times) until the filtrate is NEUTRAL to litmus paper

Question 20

why is it essential to remove NaOH completely?

Answer 20

To avoid/prevent difficulty during the recrystallization step.

Question 21

step 5 of the procedure

Answer 21

Recrystallize the product by adding 10mL of hot 95% ethanol. Stir to dissolve. U may add some more solvent but not to exceed 20 mL. Allow to cool. As soon as crystals begin to form, cool in an ice bath to complete recrystallization. Filter by SUCTION FILTRATION. Wash the product with cold ethanol using dropper

Question 22

Step 6 of the procedure

Answer 22

dry the crystals in a desiccator. weigh the dried product in the next laboratory period and calculate the percentage yield. determine the melting point and compare ur result w/ the literature value

Question 23

2 qualitative tests to perform on the product:
(1)
(2)

Answer 23

(1) Ignition test
(2) Baeyer’s test

Question 24

what will be the next and last step after performing the qualitative tests

Answer 24

run an FT-IR measurement on the product

Question 25

in the aldol condensatio, why is it essential that the aldehyde component contain none of the corresponding acid

Answer 25

because the presence of an acid group can alter the reactivity of the aldehyde, leading to different reaction pathways and products. It is also important that the aldehyde component does not contain any acud to ensure the success of the aldol condensation reaction and maximize the yield of the desired product, which is dibenzalacetone.

Question 26

in the experiment, what was the limiting reagent?

Answer 26

acetone

Question 27

Test Compound: Benzaldehyde

Ignition Test Result: ______
Baeyer’s Test Result: ________

Answer 27

• production of flame(+)
• formation of brown precipitate (+)

Question 28

Test Compound: Dibenzalacetone

Ignition Test Result: ______
Baeyer’s Test Result: ________

Answer 28

-production of flame (+)
- change in color from deep purple to brown (+)

Question 29

in the aldol condensation using the conditions of this experiment, why is it essential that the aldehyde component contain none of the corresponding acid?

Answer 29

to ensure the success of the aldol condensation reaction and maximize the yield of thebdesired product, which in this experiment is the dibenzalacetone

Question 30

title of activity #10

Answer 30

Synthesis of Dibenzalacetone: ALDOL Condensation