Basicity of Disubstituted Aromatic Amines (Resonance / Mesomeric Effect)

A Puzzle In The Basicity Of Some Disubstituted Aromatic Amines We’ve seen that several key factors influence the basicity of amines – charge, resonance, inductive effects, pi donor / pi acceptor behavior, hybridization and even the contribution of the nitrogen lone pair towards aromaticity. In isolation, each of these factors is fairly straightforward to understand.…

Read More

Amine Basicity Is Measued By The pKa Of Its Conjugate Acid (pKaH)

Quantifying The Basicity Of Amines, Using “The pKa Of The Conjugate Acid”, a.k.a. “pKaH” How do you measure the basicity of an amine? Case in point: what’s a stronger base: pyridine or piperidine? If you said piperidine, congratulations – it is indeed a stronger base. But why?  And how much stronger? How does one go about trying to…

Read More

The Robinson Annulation – Organic Chemistry

The Robinson Annulation The Robinson Annulation is the name for a process that combines two key reactions you’ve learned previously into one longer sequence. The reaction begins with a Michael reaction, followed by an intramolecular aldol condensation to give a new six-membered ring containing an alpha, beta unsaturated ketone.  This post goes into all the…

Read More

The Acid-Catalyzed Aldol Reaction

The acid-catalyzed aldol condensation begins with conversion of a ketone (or aldehyde) to an enol, which then attacks another aldehyde or ketone which has been activated by protonation of the carbonyl oxygen. This is referred to as the “aldol addition” reaction. The aldol condensation goes a step further: as the name suggests, water is removed…

Read More

D- and L- Notation For Sugars – Organic Chemistry

The D- And L- Notation For The Absolute Configuration Of Sugars And Amino Acids What differentiates “D-Glucose” from “L-Glucose” ? Or D-alanine from L-alanine? And what is this D- and L- nomenclature, anyway? Read on: 1. D- And L- Provides A Quick Shorthand For Designating Enantiomers D- and L- notation provides a quick shorthand for designating enantiomers. …

Read More

Synthesis of Peptides – Organic Chemistry

Peptide bonds: Forming peptides from amino acids with the use of protecting groups Today we’ll go deeper on how to synthesize the most important amides of all – peptides – with an important contribution from protecting group chemistry. 1. What Are Peptide Bonds? A “peptide bond” is an amide linkage (see Amides: Properties. Synthesis, and Nomenclature)…

Read More

A new portable device can reveal a chili pepper’s heat

Just how hot is your chili pepper? A new chili-shaped device could quickly signal whether adding the pepper to a meal might set your mouth ablaze. Called the Chilica-pod, the device detects capsaicin, a chemical compound that helps give peppers their sometimes painful kick. In general, the more capsaicin a pepper has, the hotter it…

Read More

Overheated plastic pipes can leak hazardous chemicals into water

In August, a massive wildfire tore through the San Lorenzo Valley north of Santa Cruz, Calif., destroying almost 1,500 structures and exposing many others to extreme heat. Before the fire was even out, lab tests revealed benzene levels as high as 9.1 parts per billion in residential water samples — nine times higher than the…

Read More

A new iron-based catalyst converts carbon dioxide into jet fuel

Today, airplanes pump a lot of climate-warming carbon dioxide into the atmosphere. But someday, carbon dioxide sucked from the atmosphere could be used to power airplanes. A new iron-based catalyst converts carbon dioxide into jet fuel, researchers report online December 22 in Nature Communications. Unlike cars, planes can’t carry batteries big enough to run on…

Read More

Supercooled water has been caught morphing between two forms

Supercooled water is two of a kind, a new study shows. Scientists have long suspected that water at subfreezing temperatures comes in two distinct varieties: a high-density liquid that appears at very high pressures and a low-density liquid at lower pressures. Now, ultrafast measurements have caught water morphing from one type of liquid to the…

Read More