A good movie stirs emotions in us. Dramatized by fine actors, the motion picture delivers a story, communicates ideas, invokes feelings, displays beauty, and sometimes hopes to change our perception. Every character is vital to the storyline and, therefore, absolute.
Around the early 1800s, scientists began to notice the presence of isomerism in all types of compounds; however, at the time, it was referred to using different names.
The term allotrope was used to describe different varieties of an element that existed in different physical forms, such as diamond or graphite for carbon or monoclinic or rhombic for sulfur. Polymorphism was used to explain compounds that occurred in more than one crystalline form, like aragonite and calcite, both crystalline forms of calcium carbonate.
Learning Objective: To study how molecular weight, molecular shape, functional group, and carbon number impact density.
Skill Level - Intermediate
Prerequisites:
Common names of alkanes
The DBE calculation uses the general molecular formula to find the presence of unsaturation in a compound. The unsaturation is calculated in levels or degrees.
The lowest degree of unsaturation (DOU) indicates minimum unsaturation, where there is the least loss of hydrogens to form a pie bond or a cyclic ring, like in cycloalkanes.
General Molecular Formula
| n- | iso- | neo- | sec- or s- | tert- or t- | |
|---|---|---|---|---|---|
| Stands for | normal | isomer | Greek for new | secondary | tertiary |
| Structure | The carbon chain is continuous without any branching; therefore, it represents a straight-chain alkane. | Iso- prefix indicates branching of the straight chain alkane.
|
| Types of Interactions | Shown By | Energy (KJ/mole) | Examples (Image) |
|---|---|---|---|
| Ion-Ion | Only Ions (E.g.- Na+Cl- or carboxylate ion and ammonium ion) | 400-4000 |  |
| Ion-Dipole | Ion and Polar molecules (E.g., Na+ and H2O) | 40-600 |
If a two-electron covalent bond breaks symmetrically, each of the two atoms receive one electron; it is a homolytic bond cleavage.
A homolytic cleavage is shown using a fish-hook arrow, which implies one-electron movement.
London dispersion forces are the weak intermolecular attractive forces that occur when the molecules are spaced closely. If the spacing is compact, the interactions are stronger. This means that the temporary dipoles induced due to the dispersion of electrons are also larger. Such a compact cluster will require more energy to break, raising the physical properties of the melting and boiling point.
Learning Objective: To get familiar with conformational isomerism, what it means, how it occurs, and also differs from other forms of isomerism.
Skill Level - Beginner
Prerequisites: