The following is a sketch of three Am (Absorbance of M) vs [M] for three different wavelengths. Which one would be best for measuring [M] at any time? Why? 545 nm Absorbance 470 nm What is the slope of each of these lines represent? 600 nm [M]
Basics in Organic Reactions Mechanisms
In organic chemistry, the mechanism of an organic reaction is defined as a complete step-by-step explanation of how a reaction of organic compounds happens. A completely detailed mechanism would relate the first structure of the reactants with the last structure of the products and would represent changes in structure and energy all through the reaction step.
Heterolytic Bond Breaking
Heterolytic bond breaking is also known as heterolysis or heterolytic fission or ionic fission. It is defined as breaking of a covalent bond between two different atoms in which one atom gains both of the shared pair of electrons. The atom that gains both electrons is more electronegative than the other atom in covalent bond. The energy needed for heterolytic fission is called as heterolytic bond dissociation energy.
Polar Aprotic Solvent
Solvents that are chemically polar in nature and are not capable of hydrogen bonding (implying that a hydrogen atom directly linked with an electronegative atom is not found) are referred to as polar aprotic solvents. Some commonly used polar aprotic solvents are acetone, DMF, acetonitrile, DMSO, etc.
Oxygen Nucleophiles
Oxygen being an electron rich species with a lone pair electron, can act as a good nucleophile. Typically, oxygen nucleophiles can be found in these compounds- water, hydroxides and alcohols.
Carbon Nucleophiles
We are aware that carbon belongs to group IV and hence does not possess any lone pair of electrons. Implying that neutral carbon is not a nucleophile then how is carbon going to be nucleophilic? The answer to this is that when a carbon atom is attached to a metal (can be seen in the case of organometallic compounds), the metal atom develops a partial positive charge and carbon develops a partial negative charge, hence making carbon nucleophilic.
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![### Absorbance of M vs. Concentration [M] at Different Wavelengths
In the diagram shown, we have three lines representing the absorbance (A_M) of a substance M at three different wavelengths (545 nm, 470 nm, and 600 nm). The x-axis of the graph represents the concentration of M ([M]), while the y-axis represents the absorbance.
#### Analysis of the Graph
1. **Wavelengths and Slopes:**
- **545 nm:** This line has the steepest slope, indicating that absorbance changes significantly with a small change in concentration.
- **470 nm:** This line has a moderate slope, showing a moderate change in absorbance with varying concentration.
- **600 nm:** This line has the shallowest slope, meaning that absorbance changes little with changes in concentration.
#### Question 1: Best Wavelength for Measuring [M]
Given the choice of wavelengths, 545 nm would be the most suitable for measuring [M] at any time. This is because the steepest slope means that even small changes in concentration will result in noticeable changes in absorbance, making it easier to detect and measure variations in [M].
#### Question 2: Meaning of the Slopes
The slope of each line represents the sensitivity of the absorbance to the concentration of M at that specific wavelength. Mathematically, the slope is the extinction coefficient (ε) in Beer-Lambert Law, given by:
\[ A = \varepsilon c \]
where:
- \( A \) is the absorbance,
- \( \varepsilon \) is the molar extinction coefficient,
- \( c \) is the concentration of the substance.
Thus, higher slopes signify higher sensitivity and larger extinction coefficients.
In summary, 545 nm provides the most sensitive measurements of M concentrations, while 600 nm is the least sensitive.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F1dedc2f0-34a2-4f6a-9bbc-fab867b2dfd0%2Fe4c54734-2f19-4947-951f-bc49bc1b6dbc%2Fleljpgn.png&w=3840&q=75)
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