What does “periplanar” mean?
‘Peri’ comes from the Greek word for ‘near’ and so periplanar means “approximately planar”. In their article “Periplanar or Coplanar?” Kane and Hersh point out that many organic textbooks use anti-periplanar to mean completely anti-planar, or anti-coplanar, which is technically incorrect.
What is periplanar conformation?
Periplanar refers to two atoms or groups of atoms in a conformation are in the same plane with respect to the reference single bond.
What is the difference between periplanar and anti-Peri planar?
In this conformation, both groups are on the same side of the molecule. Anti-periplanar refers to a periplanar conformation where the dihedral angle between two atoms or groups of atoms is between ±150° and 180°. In texts, anti-periplanar means bonds are anti-coplanar.
What is periplanar and coplanar in organic chemistry?
Illustrated Glossary of Organic Chemistry. Periplanar: Atoms, groups , bonds having a torsional angle between 0 o and 30 o ( syn-periplanar ) or between 150 o and 180 o ( anti-periplanar ). Coplanar refers to objects lying in the same plane ( torsional angle = 0 o or 180 o ).
What does syn periplanar mean?
Synperiplanar definition Filters. (chemistry) Describing a torsion angle between 0° and 30° adjective.
What is SYN periplanar in organic chemistry?
The syn-periplanar conformation is a periplanar conformation in which the dihedral angle between the atoms or groups is between ±30°. In this conformation, both groups are on the same side of the molecule.
What is SYN periplanar and anti-periplanar?
Periplanar: Atoms, groups, bonds having a torsional angle between 0o and 30o (syn-periplanar) or between 150o and 180o (anti-periplanar). Coplanar refers to objects lying in the same plane (torsional angle = 0o or 180o).
What does anti coplanar mean in organic chemistry?
In organic chemistry, anti-periplanar, or antiperiplanar, describes the A−B−C−D bond angle in a molecule. In this conformer, the dihedral angle of the A−B bond and the C−D bond is greater than +150° or less than −150° (Figures 1 and 2).
What is syn and anti elimination?
What is syn and anti elimination? In syn elimination, the base attacks the β-hydrogen on the same side as the leaving group. In anti elimination, the base attacks the β-hydrogen on the opposite side of the leaving group.
When can syn elimination occur?
When subjected to temperatures above 400 °C, esters containing β-hydrogens can eliminate a carboxylic acid through a 6-membered transition state, resulting in an alkene. Isotopic labeling was used to confirm that syn elimination occurs during ester pyrolysis in the formation of stilbene.
How do I know if I have antiperiplanar?
Antiperiplanar. If two bonds define two line segments, then they are antiperiplanar if they are antiparallel in the plane they define. It's much easier to see antiperiplanar bonds than it is to explain them.
What is anti-Periplanar elimination?
0:1519:57Organic Chemistry - Anti-periplanar Elimination Explained! - YouTubeYouTubeStart of suggested clipEnd of suggested clipIt's anti-periplanar elimination and I have for you this great example of anti-periplanarMoreIt's anti-periplanar elimination and I have for you this great example of anti-periplanar elimination you're given two molecules molecule one and molecule two they look very similar.
What is an anti conformation?
anti conformation Definition When two large groups are positioned at a dihedral angle of 180° in a staggered conformation, the product confirmation will be called Anti-conformation.
Why does E2 need anti coplanar?
E2 Reaction Coordinate It is important to note the anti-coplanar orientation of the base and the leaving group. Both the base and leaving group are electron rich and electrostatically repel each other forcing an anti-coplanar orientation between the base and leaving group.
What is a gauche conformer?
In the study of conformational isomerism, the Gauche effect is an atypical situation where a gauche conformation (groups separated by a torsion angle of approximately 60°) is more stable than the anti conformation (180°).
What is Zaitsev product?
Zaitsev's rule, based on experiment observations of the dehydration of alcohols, expresses the preference for eliminations to give the highly substituted (more stable) alkene, which may also be described as the Zaitsev product.
What is anti-periplanar?
Anti-periplanar refers to a periplanar conformation where the dihedral angle between two atoms or groups of atoms is between ±150° and 180°. In texts, anti-periplanar means bonds are anti-coplanar.
What is anti-periplanar in organic chemistry?
Two of the terms you may encounter in organic chemistry are anti-periplanar and syn-periplanar. Both refer to the geometry of chemical bonds in a molecule.
What is the anti-periplanar conformation?
The anti-periplanar conformation is a periplanar conformation in which the dihedral angle between two atoms or groups of atoms is between ±150° and 180°. In this conformation, the groups are anti-coplanar.
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Who coined the term "anti-periplanar"?
The term anti-periplanar was first coined by Klyne and Prelog in their work entitled "Description of steric relationships across single bonds", published in 1960. ‘Anti’ refers to the two functional groups lying on opposite sides of the plane of the bond.
Which mechanism prefers anti-periplanar geometry?
Figure 10: In an E 2 mechanism molecules generally prefer an anti-periplanar geometry because it aligns molecular orbitals and sets up the molecule to move electrons in a C–H bonding orbital into a π C-C bonding orbital.
What is the methyl group in pinacol rearrangement?
In the pinacol rearrangement, a methyl group is found anti-periplanar to an activated alcohol functional group. This places the σ C–C orbital of the methyl group parallel with the σ* C–O orbital of the activated alcohol. Before the activated alcohol leaves as H 2 O the methyl bonding orbital donates into the C–O antibonding orbital, weakening both bonds. This hyperconjugation facilitates the 1,2-methyl shift that occurs to remove water. See Figure 11 for the mechanism.
What is the dihedral angle of a synperiplanar conformer?
In the syn-periplanar conformer, the A and D are on the same side of the plane of the bond, with the dihedral angle of A–B and C–D between +30° and −30° (see Figure 2).
What is the anti-periplanar bond angle?
Anti-periplanar is a term used in organic chemistry to describe the A–B–C–D bond angle in a molecule. In this conformer, the dihedral angle of the A–B bond and the C–D bond is greater than +150° or less than −150° (Figures 1 and 2 ). Anti-periplanar is often used in textbooks to mean strictly anti-coplanar, with an A-B C-D dihehedral angle of 180° (Figure 3). In a Newman projection, the molecule will be in a staggered arrangement with the anti-periplanar functional groups pointing up and down, 180° away from each other (see Figure 4). Figure 5 shows 2-chloro-2,3-dimethylbutane in a sawhorse projection with chlorine and a hydrogen anti-periplanar to each other.
Can parallel orbitals be used in hyperconjugation?
The parallel orbitals can overlap and become involved in hyperconjugation. If the bonding orbital is an electron donor and the anti-bonding orbital is an electron acceptor, then the bonding orbital will be able to donate electronegativity into the anti-bonding orbital.
Which atoms must be anti-periplanar to the leaving group?
In an E2 reaction mechanism, the deprotonated hydrogen must be (1) on a neighboring carbon and (2) anti-periplanar to the leaving group. Therefore, we must identify all the hydrogen atoms in this molecule that are neighboring and anti-periplanar.
Can anti-periplanar hydrogen be found in a chair?
Determining the neighboring, anti-periplanar hydrogen (s) in a chair configuration can be very difficult. In fact, there might not even be a neighboring, anti-periplanar hydrogen. If there is no neighboring, anti-periplanar hydrogen, then the E2 reaction cannot occur. See below for an example of finding the anti-periplanar hydrogen atoms ...
Is hydrogen deprotonated or anti-periplanar?
To understand what that means, let’s break down the term anti-periplanar.
