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Related Concept Videos

Basicity of Heterocyclic Aromatic Amines01:25

Basicity of Heterocyclic Aromatic Amines

7.1K
Heterocyclic amines, where the N atom is a part of an alicyclic system, are similar in basicity to alkylamines. Interestingly, the heterocyclic amine having a nitrogen atom as part of an aromatic ring has much less basicity than its corresponding alicyclic counterpart. For this reason, as presented in Figure 1, piperidine (pKb = 2.8) is significantly more basic than pyridine (pKb = 8.8).
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Leveling Effect01:29

Leveling Effect

1.5K
In acid-base chemistry, the leveling effect refers to the limitation imposed by the solvent on the strength of acids and bases in solution. When a base stronger than the solvent's conjugate base is used, it deprotonates the solvent until the base is entirely consumed, making it ineffective against weaker acids. Conversely, an acid stronger than the solvent's conjugate acid protonates the solvent until the acid is depleted, rendering it ineffective against weaker bases. Essentially, the...
1.5K
Leveling Effect and Non-Aqueous Acid-Base Solutions02:11

Leveling Effect and Non-Aqueous Acid-Base Solutions

9.9K
This lesson defines the leveling effect in acidic and basic solutions and its role in aqueous and non-aqueous solutions. It is essential to understand the competing nature of various species in a chemical system.
The Leveling Effect of a Solvent
A generic acid (HA) reacts with the generic base (B-) to yield the corresponding conjugate base (A-) and conjugate acid (HB):
9.9K
Basicity of Aliphatic Amines01:21

Basicity of Aliphatic Amines

7.0K
Amines can behave as Brønsted–Lowry bases by accepting a proton from the acid to form corresponding conjugate acids. Due to a lone pair of nonbonding electrons, aliphatic amines can also act as Lewis bases by forming a covalent bond with an electrophile.
To measure the basicity of amines, two conventions are generally used. The first defines Kb as the basicity constant for the deprotonation reaction of water by the amine, as presented in Figure 1. Conventionally, lower Kb indicates higher...
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Solvating Effects02:12

Solvating Effects

9.1K
An understanding of the solvating effect helps rationalize the relation between solvation and acidity of the compound. In addition, this also explains the relative stability of conjugate bases for compounds with different pKa values. This lesson details, in-depth, the principle of solvating effects. The strength of an acid and the stability of its corresponding conjugate base are determined using pKa values. This observed relationship is a consequence of solvation, which is the interaction...
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Basicity of Aromatic Amines01:18

Basicity of Aromatic Amines

8.2K
The basicity of aromatic amines is much weaker than that of aliphatic amines due to the involvement of the lone pair of electrons over the N atom in resonance with the aryl rings. Generally, the electron-donating ability of any substituents on the aryl ring of aromatic amines increases the basicity of the amine by increasing electron density, and hence the availability of lone pair on the nitrogen. On the other hand, electron-withdrawing functional groups on the aryl ring of amines decrease the...
8.2K

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Light-induced Patterning and Grafting for Slippery Surfaces based on Silane-coated Nanoporous Structures
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Light-induced Patterning and Grafting for Slippery Surfaces based on Silane-coated Nanoporous Structures

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Base Layer Influence on Protonated Aminosilane Gradient Wettability.

Kayesh M Ashraf, Chenyu Wang, Sithara S Nair

  • 1Department of Chemistry, Kansas State University , Manhattan, Kansas 66506-0401, United States.

Langmuir : the ACS Journal of Surfaces and Colloids
|April 20, 2017
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Summary
This summary is machine-generated.

Researchers created protonated amine gradients on silicon wafers using controlled rate infusion (CRI). Surface properties like wettability and contact angle varied along the gradient, influenced by the base layer

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Area of Science:

  • Surface Chemistry
  • Materials Science
  • Nanotechnology

Background:

  • Tailoring surface properties is crucial for advanced material applications.
  • Gradient surfaces offer unique possibilities for controlled interactions.
  • Understanding the influence of base layer chemistry on gradient formation is essential.

Purpose of the Study:

  • To prepare protonated amine gradients on silicon wafers with varying hydrophobicity.
  • To characterize the chemical and physical properties of these gradients.
  • To investigate the impact of different base layers on gradient formation and surface characteristics.

Main Methods:

  • Preparation of hydrophobic base layers using spin coating of silane sols (TMOS, PTMOS, DMDMOS, OTMOS).
  • Formation of amine gradients via programmed controlled rate infusion (CRI) of APTEOS.
  • Characterization using X-ray photoelectron spectroscopy (XPS) and dynamic contact angle measurements (Wilhelmy plate).
  • Amine protonation using concentrated HCl vapor.

Main Results:

  • XPS confirmed gradient distribution of amine functional groups, controlled by CRI exposure time.
  • Nitrogen modification extent varied with base layer hydrophobicity; C8 base layer showed reduced nitrogen.
  • Contact angle (CA) and hysteresis were dependent on the base layer and varied along the gradient.
  • C8-derived gradients exhibited the largest CA change and approximately doubled CA hysteresis, indicating inhomogeneity.
  • Wilhelmy plate analysis revealed unique S-shaped CA distance curves for gradients, reflecting precise surface chemistry.

Conclusions:

  • Controlled rate infusion (CRI) enables precise preparation of protonated amine gradients.
  • Base layer composition significantly influences gradient formation, nitrogen incorporation, and surface wettability.
  • Dynamic contact angle measurements provide detailed insights into the chemical inhomogeneity of gradient surfaces.