Molecular Structure Of Organic Compounds Flashcards
Define organic chemistry
The study of the structure, properties, composition, reactions, and preparation (i.e. synthesis) of chemical compounds containing carbon
What are the most common atoms found in organic compounds?
Carbon, hydrogen, oxygen, nitrogen and the halides (i.e. fluorine, chlorine, bromine)
What type of bonds usually hold organic compounds together?
Usually covalent, but also ionic. Generally follow the octet rule
A carbon has what types of orbitals in its outermost shell? How many bonds does this allow it form?
One S and three P. Four single bonds
An oxygen may form how many bonds?
Two singles or one double bond
A hydrogen can form how many bonds?
Only one single bond
How many bonds can a nitrogen atom form?
Three single bonds
How many bonds are halides able to form?
Only one single bond
How might you tell if two elements have similar properties? (i.e. whether they form a tetrahedral structure)
Whether they’re in the same group or not
Sulphur is an important component in what amino acid?
Cysteine
In organic molecules, hybrid orbitals are often formed. What are these a combination of?
S and P orbitals
In a carbon atom if one S and three P orbitals are mixed, what is the result?
Four hybrid SP3 orbitals
Three hybridised SP2 orbitals result from what?
The mixing of one S and two P orbitals
Two hybridised SP orbitals results from what?
The mixing of one S and two P orbitals
What are sigma bonds? When do they form?
Those in which the electron density is between the nuclei. They are symmetric about the axis, can freely rotate, cross section would be circular.
They are formed when orbitals over lap directly
Where is the electron density in pi bonds?
Directly over and under the plane of the atoms
A single bond is what type?
A sigma bond
A double bond is what type? Triple?
A sigma and a pi. A sigma and two pi
What affect do pi bonds have on the ability of a molecule to rotate?
Much more rigid than a molecule which can rotate freely around its axis
What impact does the number of bonds have on the length?
As a rule, it makes them shorter
What is BE?
Bond dissociation energy, the energy required to break a bond. Varies with the number of bonds
What are the BE values of sigma and pi bonds respectively?
110 kcal/mole.
60 kcal/mole
What are the two ways that the delocalisation of charges in pi bonds can be represented? Describe each
Molecular orbit approach. Like a graphical representation where p orbitals and pi bonds are merged into a graphic which takes up the length of molecule, shows electron density.
Resonance approach. A series of formula-type equations showing location of charge at different times, need to be taken collectively
When does the octet rule fail?
In elements in the third row (Si, P, S, Cl) use d-orbitals and thus can have more than eight electrons in their outer shell
