Introduction to organic Chemistry Flashcards
What is an aliphatic compound
Straight chain or branched organic compounds and also included cyclic organic compounds that do not contain benzene rings.
What is a single covalent bond?
A bond made up of a pair of electrons shared between two atoms.
What is a sigma bond?
A single covalent bond formed by the “end-on” overlap of atomic orbitals.
What is a pi bond?
A covalent bond formed by “sideways” overlap of p and p or p and d atomic orbitals.
What are structural isomers?
Structural isomers are compounds with the same molecular formula but different structural formula.
There are 3 types of structural isomers:
1) Position isomerism
2) Functional group isomerism
3) Chain isomerism
What is position isomerism?
In position isomerism, it is the location of the functional group that varies in each isomer.
What is functional group isomerism?
In functional group isomerism, there are different functional groups present and therefore often have very different chemical properties.
What is chain isomerism?
Chain isomers differ in the structure of their carbon skeleton.
What is stereoisomerism?
Sterioisomers are compounds whose molecules have the same atoms bonded to each other in the same way, but with a different arrangement of atoms in space so that the molecules cannot be superimposed on each other.
- Geometrical (cis/trans) isomerism
- Optical isomerism
What is geometrical isomerism
Shown only by alkenes
Arises due to restriction of double bond
Only possible when each carbon has 2 different groups
cis-trans isomers have different b.p.
cis isomers have higher dipole
trans isomer of symmetrical alkene has zero dipole
In cis-1,2-dibromoethene both the Br atoms remain fixed on the same side of the C=C double bond where as in trans-1,2-dibromoethane, the Br atoms are positioned across the C=C double bond.
What is optical isomerism
Arises from different arrangement of atoms or groups in 3D space resulting in two isomers
Have effect on polarised light
Chiral carbon: a carbon having 4 single bonds and 4 different atoms or groups
Isomers non-super-imposable images of each other
Have same physical and chemical properties
No. of optical isomers in a molecule containing n chiral carbons =2^n
What are enantiomers?
Enantiomers are a pair of optically active molecules whose mirror images cannot be superimposed.
What is homolytic fission?
In this type of bond breaking, both the atoms at each end of the bond leave with one electron from the pair that formed the covalent bond. The species produced when a bond breaks homolytically are called free radicals.
We can show the formation of free radicals by using an equation:
HCl➡️H. + Cl.
What is heterolytical fission?
In heterolytical fission the more electronegative atom takes both electrons in the covalent bond. A small curly arrow is used to show the movement of a pair of electrons.
For example:
H-Cl ➡️ H+ + Cl-
What is a free radical reaction?
A three step reaction:
- Initiation step: the formation of free radicals to start a reaction off.
- Propagation steps: steps in a mechanism that regenerate more free radicals.
- Termination step: the final step in a mechanism, when two free radicals meet and form a product molecule.
