Orbitals of Alkene

Alkene is a hydrocarbon with a double bond two carbon atoms. Before we can go further on the reactions of alkene. Let's briefly talk about the orbitals of a alkene.

Orbitals
A double consists of one sigma bond and one pi bond. There are 4 electrons in a double bond.
 
Sigma Bond: There are 6 electrons in a carbon atom: 2 in the s orbitals and 4 in the p orbitals. Take a look of ethene, one carbon is bonded to a carbon and to two hydrogen atoms and there is no lone pair of electrons at the carbon. This implies a sp2 hybridization (120ยบ bond angle). Each C-H sigma bond is the overlap of a sp2 hybridized orbital on carbon with the 1s orbital on hydrogen.
There is also a overlap of the sp2 hybridized orbital between the two carbon (yes, the C-C double bond has one sigma bond). This sigma bond here is shorter than the sigma bond fond in ethane because it has more s character (sp2 hybridized) than the sp3 hybridized.

Pi Bond: There is an unhybridized p orbital in each carbon atom and they overlap to form a pi bond. The p orbitals have to be parallel to each other to overlap. This orientates the the C-H sigma bond in a plane. Also, a pi bond cannot rotate like a sigma bond does.


Comments

Post a Comment

Popular posts from this blog

What is Pepsin?

Image
In Your Body... Pepsin is a digestive enzyme that performed the best in the acidic condition (pH 2) produced by the gastric juice. It digests and breaks down protein (e.g. meat, seeds, eggs, dairy products, etc.). Keep in mind that pepsin digests proteins (not carbohydrates, not fat) into peptides. These peptides are then either absorbed in the intestine or further break down by enzymes from pancreas. In small intestine (pH around 7), pepsin is no longer effective and no longer digests proteins. Hormones Hormones that regulate digestion and hunger such as gastrin and secretin stimulates the production of pepsinogen, the proenzyme of pepsin. In other words, when pepsinogen is activated, it becomes pepsin.
Read more

Intro to 4 Basic Types of Reaction: SN1 SN2 E1 E2 - Updated 2024!

Image
After introducing electrophile and nucleophile, let's talk about SN1 , SN2 , E1 and E2 . Let's see what they mean first: SN1: First-Order Nucleophilic Substitution SN2: Second-Order Nucleophilic Substitution E1: First-Order Elimination E2: Second-Order Elimination   So basically, these 4 types of reactions are categorized into   Nucleophilic Substitution and Elimination .  Nucleophilic Substitution means one thing is substituted by something else, which is a nucleophile (to make it nucleophilic) Elimination always form a double bond product because as something is eliminated, the remained  electrons form a double bond  The condition for each of these reactions are different (solvent, leaving group, reactant bulkiness, etc) and the ability to classify them is crucial. Here is a table summarized all we need to know about them.   source: www.pinstopin.com Our team at Chemistery uses NordVPN every day and we highly recommend it.
Read more

E1 E2 Comparison

Image
Let's compare E1 and E2 in the following aspects: Base Substrate Solvent Leaving Group Kinetics Stereochemistry Rearrangements  Base E1: As the base abstracts the proton only after the carbocation intermediate is formed, it does not affect the rate of reaction, hence not important. E2: A strong base is indeed needed to promote the one-step reaction. Substrate E1: A more substituted substrate stabilizes the carbocation intermediate.  E2: A more substituted substrate forms a more substituted alkene.  Solvent E1: A polarizing solvent enhances the rate of ionization as it pulls the cation and anion apart.  E2: The transition state is less sensitive to the solvent as the transition state has its negative charge shared over the whole molecule.  Leaving Group Both reactions need a good leaving group.  Kinetics E1: The rate is only determined by the substrate as it is the only molecule that ionizes. E2: Both the substrate and the base affects the rate of the conc
Read more