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Organic Chemistry
Ch. 3
30
Chemistry
Undergraduate 2
10/06/2007

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Term
Conformations
Definition

Different spatial arrangements of a molecule that are generated by rotation about single bonds.

 

Rotation about C-C single bonds is very fast, hundreds of thousands of times per second at room tempterature. 

Term
Conformational analysis
Definition
The study of how ________ factors affect the structure of a molecule and its physical, chemical, and biological properties.
Term
Staggered confirmation
Definition
Conformation of the type in which the bonds on adjacent carbons are as far away from one another as possible
Term
Eclipsed confirmation
Definition
Conformation in which bonds on adjacent atoms are aligned with one another.
Term
Gauche
Definition
Term describing the position relative to each other of two substituents on adjacent atoms when the angle between their bonds is on the order of 60 degrees.
Term
Anti
Definition
Term describing relative position of two substituents on adjacent atoms when the angle between their bonds is on the order of 180 degrees
Term
Torsional strain
Definition
Decreases stability of a molecule associated with eclipsed bonds.
Term
Steric strain
Definition
Destabilization of a molecule as a result of van der Waals repulsion, distorted bond distances, bond angles, or torsion angles.
Term
Activation energy
Definition
Molecules must become energized to undergo a chemical reaction. Kinetic (thermal) energy is absorbed by a molecule from collisions with other molecules and transformed into potential energy
Term
Transition state
Definition
The point of maximum potential energy in an elementary step of a reaction mechanism as they proceed to products.
Term
van der Waals strain
Definition
Destabilization that results when two atoms or groups approach each other too closely. Also known as ___ __ _____ repulsion.
Term
Steric hindrance
Definition
An effect on structure or reactivity that depends on van der Waals repulsive forces
Term
Angle strain
Definition
The strain a molecule possesses because its bond angles are distorted from their normal values
Term
Half-chair
Definition
One of the two most stable conformations of cyclopentane. Three consecutive carbons in the half-chair conformation are coplanar. The fourth and fifth carbon lie, respectively, above and below the plane.
Term
Envelope
Definition
One of the two most stable conformations of cyclopentane. Four of the carbons in the envelope conformation are coplanar; the fifth carbon lies above or below this plane.
Term
Chair
Definition
The most stable conformation of cyclohexane
Term
Boat
Definition
An unstable conformation of cyclohexane
Term
Twist boat/skew boat
Definition
An unstable conformation of cyclohexane. It is slightly more stable than the boat conformation
Term
Axial hydrogens
Definition
the Hs are bonded parallel to a vertical axis
Term
Equatorial hydrogens
Definition
the Hs are bonded along the molecule's "equator"
Term
Ring inversion, chair-chair introversion, ring flipping
Definition
One chair conformation is converted to another chair
Term
Intermediate
Definition
Transient species formed during a chemical reaction. Typically, an intermediate is not stable under the conditions of its formation and proceeds further to form the product. Unlike a transition state, which corresponds to a maximum along a potential energy surface, an intermediate lies at a potential energy minimum.
Term
1,3-diaxal repulsions
Definition
n
Term
cis

trans
Definition
this side

across
Term
Stereoisomers
Definition
Isomers with the same constitution but that differ in respect to the arrangement of their atoms in space.
Term
Bridged compound
Definition

Two atoms are common to two (or more) rings.

 

Numbering starts with the largest bridge, then middle, then shortest. 

Term
Spiro compound
Definition

A compound in which a single carbon is common to two rings.

 

The rings are at right angles to each other.

 

Simplest example is ___ [2.2] pentane 

Term
Heterocycle
Definition
A ring that contains at least one herteratom is called a _____.  A subtance that includes an atom other than carbon, called a heteroatom, as part of a ring.
Term
Heterocyclic compound
Definition
Cyclic compound in which one or more of the atoms in the ring are elments other than carbon. Heterocyclic compounds may or may not be aromatic. Many contain double bonds. The "other" atoms are commonly O, N, and S.
Term
Fused ring compound     
Definition

Under bridged ring category.

Two rings share a common side. 

Bridge is common side, counts for zero atoms. 

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