Bonding Flashcards
Carbon atoms - when does a tetrahedral shape form?
When the carbon has 4 single bonds
Carbon atoms - when does a trigonal planar shape form?
When the carbon has 2 single bonds and 1 double bond
Carbon atoms - when does a linear shape form?
When the carbon has 1 single bond and 1 triple bond
What are the four types of intermolecular bonding in order of increasing bond strength?
Dispersion forces, dipole-induced dipole interactions, dipole dipole interactions and hydrogen bonding.
How do dispersion forces form?
Two polarisable atoms or molecules induce brief dipole moments in each other
How do dipole dipole interactions form?
Oppositely charged dipoles attract each other; the stronger the dipole moment, the stronger the interaction.
How do hydrogen bonds form?
H has unusually strong dipole moments when bonded to F, O or N allowing strong interactions with other lone pairs
Formal charge
The charge assigned to an atom in a molecule, the addition of all formal charges gives the overall charge of the molecule.
= valence - lone - 1/2 shared
Describe liquid crystals.
Crystal molecules that are considered liquid due to their ability to flow and change shape.
Describe nematic liquid crystals.
Nematic crystals are aligned with no layering and therefore allow the passage of light.
Describe smectic liquid crystals.
Smectic crystals are aligned with layering and therefore do not allow the passage of light. Applying voltage forces liquid crystals into the smectic shape.
What is an isomer?
Two or more compounds with the same chemical formula but different structures
Describe the difference between cis- face and trans- face isomers
Cis- face, the groups of interest are on the same side of the molecule. Trans- face, the groups of interest are on opposite sides of the molecule.
What are enantiomers?
Chiral isomers. I.e. Molecules with the same formula but asymmetric structures. E.g. Thalidomide (morning sickness drug)
Explain the significance of isomers/enantiomers
The shape a molecule is important for enzyme catalysed reactions, where the involved substrate and enzyme must be of certain shapes for the reaction to successfully precede (i.e. Lock and key)
