Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

OrgBio Chem > Experiment 5: Formaldehyde and Aromatic Aldehyde > Flashcards

Experiment 5: Formaldehyde and Aromatic Aldehyde Flashcards

1
Q

In Experiment 5, what class of organic compounds are being tested?

A

Aldehydes (both aliphatic & aromatic) and Ketones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What do Aldehydes and Ketones have in common?

A

They are both organic compounds with the functional carbonyl group or C=O

Aldehydes: CHO
Ketones: COR

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is an Aromatic Aldehyde?

A

The compounds in which the aldehyde functional group is attached to the aromatic ring

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Aliphatic Aldehydes vs Aromatic Aldehydes:

A

Aliphatic aldehydes are more reactive than aromatic aldehydes.

Aromatic aldehydes are less reactive due to their stability.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

PREPARATION OF FORMALDEHYDE FROM METHANOL: Procedure & Equation

A

PROCEDURE:

  1. A copper spiral is heated in the burner’s oxidizing flame.
  2. It is then dipped into a solution of 1 mL methyl alcohol / CH3OH in 5-6 mL of H2O.

EQUATION:

2 CH3OH + O2 [Cu]–> 2 HCHO + 2 H2O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How was CH2O / HCHO produced?

A

It was produced by the oxidation of methanol.

Methanol loses an H atom and gains an O atom –> OXIDATION

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

In preparation of HCHO, what was the catalyst?

A

Cu from the copper spiral

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Formaldehyde vs Formalin

A

Formaldehyde is a gas at room temperature. It is neutral and soluble in water.

Formalin is a solution of 37-40% formaldehyde in water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

5.1A. SCHIFF’S TEST: Procedure

A

PROCEDURE:

1 mL of colorless Schiff’s Solution / C20H20N3 HCl is added to three different test tubes containing

  • HCHO
  • C6H5CHO / benzaldehyde
  • CH3COCH3 / acetone
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

5.1B. Why is C20H20N3 HCl colorless? What was its original color?

A

C20H20N3 HCl was originally magenta-red because it contained fuchsin which gave it its color.

However, it was decolorized by sulfurous acids / sulfur dioxide, making it lose its color

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

5.1C. SCHIFF’S REST: Results & Discussion

A
  • Schiff in HCHO: Saturated magenta color
  • Schiff in C6H5CHO: Pale pink bubble on liquid

When aldehydes react with Schiff’s reagent, they restore the fuchsin’s magenta color.

  • Schiff in CH3COCH3: Remains purple

Ketones do not give this color.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

5.1D. Why does Schiff’s only work with aldehydes?

A

The free and uncharged amine groups in the reagent react with the aldehyde groups to form aldimine, which further reacts into a bisulfite ion. Finally, the magenta bisulfite adduct is formed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

5.2A. RESORCINOL TEST: Procedure

A

PROCEDURE:

  1. HCHO (formalin) is added with resorcinol solution / C6H6O2.
  2. The test tube is then inclined and added with conc. H2SO4.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

5.2B. RESORCINOL TEST: Results & Discussion

A

A red flocculent precipitate line forms at the junction of two layers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

5.2C. What is the Resorcinol Test specifically used to test for?

A

The presence of formaldehyde / HCHO

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

5.2D. Resorcinol is often utilized with formaldehyde to manufacture _____

A

Resins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

These two solutions are mild oxidizing agents

A
  1. Tollen’s solution
  2. Fehling’s solution
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

5.3A. What is the other name of the Silver Mirror Test?

A

Tollen’s Test

19
Q

5.3B. SILVER MIRROR TEST: Procedure

A

PROCEDURE

  1. 2 mL of ammoniacal silver nitrate / Ag(NH3)2NO3 is added into three different test tubes containing HCHO, C6H5CHO & CH3COCH3 each.
  2. Agitate all mixtures thoroughly then warm in a water bath.
20
Q

5.3C. What formed when Ag(NH3)2NO3 was exposed to aldehydes, and why?

A

Silver mirror-like substances formed. This is because the silver ions were reduced

Ketones do not give this result.

21
Q

5.3D. Aside from the reduction of silver ions, what occurs when aldehydes are exposed to Ag(NH3)2NO3?

A

If an aldehyde is present in ammoniacal silver nitrate, it is readily oxidized by the reagent into its corresponding carboxylic acid

-CHO oxidized to -COOH

Ketones do not give this result

22
Q

5.3E. SILVER MIRROR TEST: Equations & Results

A

HCHO + Ag(NH3)2 + 3 OH –> HCOOH / Formic Acid + 2 Ag + 4 NH3

C6H5CHO + Ag(NH3)2 + 3 OH –> C6H5COOH / Benzoic Acid + 2 Ag + 4 NH3

CH3COCH3+ Ag(NH3)2 + 3 OH –> No reaction

23
Q

5.4A. HCHO ON PROTEIN SUBSTANCES: Procedure

A

PROCEDURE:

  1. Two gelatin sheets are prepared.
  2. One sheet is placed in 1 mL formalin in water, while the other is placed in water only. Allow them to stand.
  3. Test their solubility in hot water.
24
Q

5.4B. What was the purpose of the gelatin sheets?

A

They were used as protein.

25
5.4C. HCHO ON PROTEIN SUBSTANCES: Results & Discussion
- The first gelatin sheet exposed to the **formalin-H2O solution** ***solidified more*** and sank to the bottom. - The second gelatin sheet exposed **only to water** ***softened*** and **did not sink** to the bottom.
26
5.4D. Why did the gelatin sheet harden when exposed to HCHO only?
Formaldehyde is known for its ability to **deactivate or immobilize proteins**. **Crosslinking** occurs between formalin and the gelatin upon interacting, leading to a **decrease** in the sheet’s **swelling and solubility**
27
5.5A. FEHLING'S TEST: Procedure & Equation
**PROCEDURE:** 1. 1 mL of **Fehling's solution / Cu(OH)2** is added to three different test tubes, each containing **HCHO, C6H5CHO & CH3COCH3**. 2. All test tubes are put in a **warm water bath**. **EQUATION:** *for HCHO only* HCHO + Cu(OH)2 --> HCOOH + Cu2O + H2O
28
5.5B. Fehling's solution is a **mixture** of:
- Copper sulfate / **CuSO4** - Sodium hydroxide / **NaOH** - **Rochelle Salt** or **Sodium Potassium Tartrate**
29
5.5C. FEHLING'S TEST: Results & Discussion
- **HCHO in Cu(OH)2** resulted in the formation of **red precipitates**, indicating a **positive reaction** - **C6H5CHO in Cu(OH)2** and **CH3COCH3 in Cu(OH)2** yielded **no reaction**; thus solution **remained blue**. *This is because **ketones** and **aromatic aldehydes** do not work with Fehling's solution*
30
5.5D. What happens when **aliphatic aldehydes** interact with **Cu(OH)2**?
**Aliphatic Aldehydes are oxidized** in the reaction with Fehling’s solution, leading to the formation of **red precipitate**
31
5.5E. How does **Cu2O** become a byproduct in Fehling's test?
This is because the copper (II) ions from Fehling’s reagent are **reduced** to **Cu2O / cuprous oxide** ions
32
5.6A. AUTOXIDATION OF C6H5CHO: Procedure & Equation
**PROCEDURE**: 1. Place a **few drops of C6H5CHO** on a watch glass. 2. Expose to the **atmosphere**. **EQUATION**: C6H5CHO *[O2]—>* **C6H5COOH / Benzoic acid**
33
5.6B. What did C6H5CHO oxidize to?
**C6H5COOH** or Benzoic Acid in the form of **crystals**
34
5.6C. What is **Autoxidation**?
The **spontaneous oxidation** of a compound in the presence of **oxygen**
35
5.6D. Why did C6H5CHO autoxidize easily and form crystals?
- Benzaldehyde, as an **aldehyde**, autoxidizes easily because of its **present H atom** bonded to its **carbonyl functional group** - It formed crystals because of its **acidic nature**
36
5.7A. ADDITION OF SODIUM BISULFITE: Procedure & Equation
**PROCEDURE**: 1. 1 mL of cold **conc. sodium bisulfite / NaHSO3** is added to 0.5 mL of **CH3COCH3** 2. Shake vigorously. **EQUATION**: CH3COCH3 + NaHSO3 —> CH3-C-**OH**-**SO3Na**CH3
37
5.7B. What formed after NaHSO3 was added?
Bubble layer and **white precipitates** PPT is called CH3-C-**OH**-**SO3Na**CH3 or **Acetone sodium bisulfite**
38
5.7C. How was **acetone sodium bisulfite** formed?
The carbonyl group in acetone is **highly polar**. This causes the **nucleophile NaHSO3** ***to form a bond*** with the **electrophilic C=O functional group**. The alkoxide is then **protonated** by the **addition of an acid** to form an alcohol
39
5.8A. FORMATION OF PHENYLHYDRAZONE: Procedure & Equation
**PROCEDURE**: 1. 3 drops of **CH3COCH3** are added with **2,4-dinitrophenylhydrazine / C6H6N4O4**, then shaken. **EQUATION**: CH3C**O**CH3 + C6H6**N4O4** —> CH3-C=**N2C6H6**CH3
40
5.8B. What was the reaction after **C6H6N4O4** was added?
The solution’s texture **thickened**, and an **orange-yellow precipitate** formed CH3-C=**N2C6H6**CH3 or **Acetone 2,4-dinitrophenylhydrazone**
41
5.8C. What does the orangish color of acetone 2,4-dinitrophenylhydrazone precipitate indicate?
That the **original carbonyl group** in acetone was **non-conjugated**
42
5.9A: IODOFORM TEST: Procedure & Equation
**PROCEDURE**: 1. In a test tube with **CH3COCH3**, add 8 drops of **10% NaOH**. 2. Then, slowly add drop-by-drop **I2**. **EQUATION**: CH3COCH3 [I2 & NaOH]—> **CHI3** + CH3COONA
43
5.9B. What is Iodoform Test applied to?
The test is applied to identify **methyl ketones**
44
5.9C. What forms in Iodoform Test, and what is it the result of?
The successful **transformation** of CH3COCH3 to **CH3COONa** results in the formation of **yellow precipitates** called **Iodoform / CHI3**

OrgBio Chem (21 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions