Bromophenol blue (BPB) is a pH indicator that turns yellow below pH 3.0 and blue above pH 4.6. It is commonly used in molecular biology as a tracking dye for DNA electrophoresis.
| IUPAC Name | 3′,3″,5′,5″-tetrabromophenolsulfonephthalein |
| Molecular Formula | C19H10Br4O5S |
| CAS Number | 115-39-9 |
| Synonyms | 3′,3″,5′,5″-Tetrabromophenolsulfonphthalein, TBB, Bromophenol Blue Sodium Salt, and Bromphenol blue free acid |
| InChI | InChI=1S/C19H10Br4O5S/c20-13-5-1-12(2-6-13)19(11-24)27(25,26)17-9-15(29(21,22)23)7-3-14(17)18(10-16(19)30(25,26)28)31(4-8-32(25,26)27)33(34)35/h1-10,24H,11H2,(H,21,22,23) |
Bromophenol Blue Molar Mass
BPB has a molar mass of 669.96 g/mol. Molar mass refers to the mass of one mole of a substance, expressed in grams per mole. The molar mass of a compound can be calculated by adding the atomic masses of each of its constituent atoms. BPB is a complex organic compound that contains carbon, hydrogen, oxygen, sulfur, and bromine atoms, and its molar mass is calculated by adding the atomic masses of each of these elements in the compound.
Bromophenol Blue Boiling Point
BPB has a boiling point of approximately 600°C. The boiling point of a substance is the temperature at which the vapor pressure of the substance is equal to the atmospheric pressure. At this temperature, the liquid changes to its gaseous state. BPB has a high boiling point due to its large size and complex structure, which requires a significant amount of energy to break the intermolecular forces holding the molecules together.
Bromophenol Blue Melting Point
BPB has a melting point of approximately 218°C. The melting point of a substance is the temperature at which the solid form of the substance changes to its liquid form. The melting point of BPB is relatively high due to the strong intermolecular forces present in the crystal lattice.
Bromophenol Blue Density g/ml
BPB has a density of approximately 1.8 g/ml. Density is a physical property that describes the amount of mass per unit volume of a substance. The density of BPB is relatively high due to its complex structure, which results in a high mass per unit volume.
Bromophenol Blue Molecular Weight
The molecular weight of BPB is 669.96 g/mol. Molecular weight is the sum of the atomic weights of all atoms in a molecule. The molecular weight of a substance is used in various calculations, such as determining the amount of substance required to prepare a given concentration of a solution.
Bromophenol Blue Structure
BPB has a sulfonephthalein structure that contains four bromine atoms, two phenol groups, and a sulfonate group. The molecule has a central carbon atom that is connected to two phenol groups and a sulfonate group. The molecule also contains two bromine atoms attached to each of the phenol groups. The sulfonate group is negatively charged, which makes BPB a water-soluble dye.
Bromophenol Blue Formula
The chemical formula of BPB is C19H10Br4O5S. The formula represents the composition of the molecule in terms of the number and type of atoms present. The formula indicates that BPB contains 19 carbon atoms, 10 hydrogen atoms, four bromine atoms, five oxygen atoms, and one sulfur atom.
| Appearance | Dark blue crystals or powder |
| Specific Gravity | 1.82–1.85 g/cm³ |
| Color | Dark blue |
| Odor | Odorless |
| Molar Mass | 669.96 g/mol |
| Density | 1.8 g/cm³ |
| Melting Point | ~218 °C |
| Boiling Point | ~600 °C |
| Flash Point | Not applicable |
| Water Solubility | Soluble in water |
| Solubility | Soluble in ethanol, DMSO, and DMF |
| Vapor Pressure | Not applicable |
| Vapor Density | Not applicable |
| pKa | 4.0–5.6 |
| pH | 3.0 (yellow)–4.6 (blue) |
Bromophenol Blue Safety and Hazards
BPB is a relatively safe compound when handled properly. It is not classified as a carcinogen, mutagen, or teratogen. However, as with all chemicals, it is important to take appropriate precautions when handling BPB. It may cause skin irritation and eye irritation upon contact. Ingestion may cause nausea and vomiting. In case of contact with skin, wash with plenty of soap and water. In case of contact with eyes, rinse thoroughly with water for several minutes. It is also important to avoid inhalation of dust or vapors and to use proper protective equipment, such as gloves and goggles, when handling BPB.
| Hazard Symbols | None |
| Safety Description | S24/25 – Avoid contact with skin and eyes |
| S36/37/39 – Wear suitable protective clothing, gloves, and eyewear | |
| UN IDs | Not regulated |
| HS Code | 2934.99.9000 |
| Hazard Class | Not classified |
| Packing Group | Not applicable |
| Toxicity | LD50 (oral, rat): >5,000 mg/kg |
Bromophenol Blue Synthesis Methods
There are several methods to synthesize Bromophenol blue.
One common method is the reaction between 3,5-dibromo-4-hydroxybenzaldehyde and 4-aminophenol in the presence of sodium hydroxide. This reaction leads to the formation of bromophenol blue as a blue-green solid. The product can be purified by recrystallization from water or ethanol.
Another method involves the reaction between 4-dimethylaminobenzaldehyde and 3,5-dibromosalicylic acid in the presence of acetic anhydride and sulfuric acid. This reaction yields bromophenol blue as a blue solid, which can be purified by recrystallization from ethanol.
Another method involves the reaction between 3,5-dibromo-4-hydroxybenzoic acid and 4-aminophenol in the presence of sodium hydroxide. This reaction leads to the formation of a blue-green solid, which can be purified by recrystallization from water or ethanol.
Bromophenol Blue Uses
Bromophenol blue has a variety of uses in different fields due to its unique properties. Here are some of the major uses of bromophenol blue:
- Biological Staining: Used as a biological stain in electrophoresis applications. Used as a tracking dye to monitor the progress of protein or nucleic acid migration during gel electrophoresis.
- pH Indicator: Used as a pH indicator, with a transition range between pH 3.0 and 4.6. It changes color from yellow to blue as the pH of the solution increases.
- Chemical Indicators: Used as a chemical indicator to detect the presence of weak acids and bases in solutions. Used to determine the endpoint of acid-base titrations.
- Laboratory Reagent: Used as a reagent in laboratory experiments, especially those involving the determination of protein concentration.
- Medical Applications: Used in medical applications as a diagnostic tool. Used to test for the presence of protein in urine or to monitor the effectiveness of kidney dialysis.
Overall, bromophenol blue is a versatile compound with a wide range of applications in various fields, including biology, chemistry, and medicine.
Questions:
Q: Why is bromophenol blue added to the individual DNA samples?
A: Bromophenol blue is often added to individual DNA samples in gel electrophoresis experiments as a tracking dye. It allows researchers to monitor the progress of DNA migration through the gel and identify when the DNA has reached the end of the gel.
Q: What do you think causes the bromophenol blue in the sample buffer to appear yellow, and why?
A: The BPB in the sample buffer appears yellow because it is in its acidic form. Bromophenol blue is a pH indicator that changes color from yellow to blue as the pH of the solution increases. In the sample buffer, the pH is usually acidic, causing the bromophenol blue to appear yellow.
Q: What is the purpose of the bromophenol blue dye in the samples?
A: The purpose of the bromophenol blue dye in the samples is to monitor the progress of DNA migration during gel electrophoresis experiments. The bromophenol blue serves as a tracking dye, allowing researchers to see the movement of the DNA through the gel and determine when the DNA has reached the end of the gel. This helps to ensure that the experiment is proceeding as expected and allows researchers to analyze the results of the experiment.