Why is there a +R or -R effect?

In summary, the +R or -R effect refers to the presence or absence of a certain type of chemical modification on a molecule, which can significantly impact its properties and behavior. This effect is caused by the electron-donating or electron-withdrawing nature of the functional group, and can impact a molecule's reactivity, stability, and physical properties. It can often be predicted based on the position and nature of the functional group, but can also be influenced by other factors. The +R or -R effect is an important concept in organic chemistry and is commonly used in the design and synthesis of new molecules for various purposes.
  • #1
kay
60
2
What I mean to say is that why are some substituent groups such that(during resonance) the pi electrons' delocalisation is directed away from it while some groups are such that delocalisation of pi electrons is towards those groups?
Can you kindly give some examples too?
 
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  • #2
+R groups have excess electrons like -OH, -OR, -SH, -SR, -NH2, -NR2 etc.
and -R have deficit of electrons like -NO2, Carbony group (C=O), -C≡N, -COOH, -SO3H, CO₂ , SO₂ etc.
 

FAQ: Why is there a +R or -R effect?

1. Why is there a +R or -R effect?

The +R or -R effect refers to the presence or absence of a certain type of chemical modification on a molecule. This modification, known as a functional group, can have a significant impact on the properties and behavior of the molecule.

2. What causes a +R or -R effect?

The +R or -R effect is caused by the electron-donating or electron-withdrawing nature of the functional group. Electron-donating groups, denoted by +R, have a tendency to push electrons towards the rest of the molecule, while electron-withdrawing groups, denoted by -R, have a tendency to pull electrons away from the rest of the molecule.

3. How does the +R or -R effect impact a molecule?

The +R or -R effect can impact a molecule in a variety of ways, including its reactivity, stability, and physical properties. For example, a molecule with a +R effect may be more reactive and less stable, while a molecule with a -R effect may be less reactive and more stable.

4. Can the +R or -R effect be predicted?

Yes, the +R or -R effect can often be predicted based on the position of the functional group in the molecule and its electron-donating or electron-withdrawing nature. However, factors such as nearby groups or the overall structure of the molecule can also influence the strength and direction of the effect.

5. How is the +R or -R effect used in chemistry?

The +R or -R effect is an important concept in organic chemistry, as it helps predict and explain the behavior of molecules. It is also commonly used in the design and synthesis of new molecules for specific purposes, such as in pharmaceuticals or materials science.

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