Lecture 1: Introduction Flashcards
What is the acetal functional group?
C-O-C-O-C (two ethers on one carbon)
Define nucleophile.
A nucleophile is an electronegative functional group which has an electron pair that can be used to form a covalent bond.
Define electrophile.
An electrophile is an electron deficient functional group which can accept a pair of electrons to form a covalent bond; must possess an empty orbital.
Define polarised bonds.
When the electrons are not shared evenly between the two joined atoms i.e. the bond has a dipole moment.
Define polarizability.
A measure of the ease of change of electron distribution.
Define electronegativity.
A measure of how strongly the atom attracts electrons.
What if the purpose of hybridised orbitals?
Hybridised orbitals helps us to understand shapes and reactivity, without having to work out molecular orbitals. It is very difficult to solve molecular orbitals past very small molecules and is basically important for biological polymers.
What is hybridisation?
Mixing atomic orbitals to make hybrid orbitals. The energy of the orbitals don’t change. If you start with 4 atomic orbitals, 3 p orbitals and 1 s orbital, you get sp3 hybridisation. If you hydribise 2 p orbitals and 1 s orbital, you get sp2 hybridisation. The remaining pz orbital can overlap another pz orbital to form a pi bond.
What are the shapes of molecules with a) sp3 and b) sp2 hybridisation?
a) sp3 hybridisation leads to tetrahedral molecules (109.5 degree bond angles)
b) sp2 hybridisation leads to trigonal planar molecules (120 degree bond angle), with pz orbitals sticking out above and below the plane (90 degrees to the plane).
What is the shape, hybridisation and reactivity of alcohols?
Shape: tetrahedral
Hybridisation: sp3
Reactivity: nucleophile (lone pair)
What is the shape, hybridisation and reactivity of ethers?
Shape: tetrahedral
Hybridisation: sp3
Reactivity: unreactive, increases stability of organic molecules, its lone pairs are used in hydrogen bonds
What are tautomers?
Tautomers are structural isomers that differ only in the position of a hydrogen and a double bond; tautomerisation is the transformation of one tautomer to the other.
What are resonance hybrids?
When more than one arrangement of double bonds needs to be drawn in order to show the electronic distribution; we say the molecule exists as a resonance hybrid.
What is aromaticity?
To be aromatic a compound must be planar, cyclic and have (4n + 2) delocalised pi electrons, where n is an integer.
