C. Chemistry Flashcards
How do you calculate formal charges?
FC= VE – (b+ lone elctrons)
Where b is number of bonds
Priority groups in descending order:
- Quaterary ammonium cation suffix: ammonium
- Quaternary phosphonium cation suffix: phosphonium
- Teriary sulphonium cation suffix : Sulphonium
- Carboxcylic acid suffix: -oic acid
- Acid anhydride suffix: -oic anhydride
- Ester suffix: alkyl -oate
- Acyl halides: -oyl halide
- Primary amide
- Secondary amide
- Teriary amide
- Nitrile suffix: -nitrile prefix: cyano-
- Aldehyde suffix: -al prefix: formyl-
- Ketone suffix:-one
- primary alcohol
- secondary alcohol
- tertiary alcohol
- primary amine
- secondary amine
- tertiary amine
- Ether
- alkene
- alkyne
- halides Prefix:
Halo- - nitro
- alkanes suffix: -ane prefix: alkyl-
How does sp3 hybridisation work?
- Promotion of one elctron from s orbital to p orbital
- hybridisation-where the orbitals mix to form hybrid orbitals with different energy
- sp3= s+p+p+p
- therefore 25% s and 75% p so the hybrid orbitals are closer to the p orbitals as 2s is promoted to a higher energy level
- so all the p orbitals are used and the s orbital
How doe sp2 hybridisation work?
- Promotion of one elctron from s orbital to p orbital
- hybridisation-where the orbitals mix to form hybrid orbitals with different energy
- sp2= s+p+p
- therefore 33% s and 67% p so the hybrid orbitals are closer to the p orbitals as 2s is promoted to a higher energy level
- so two p orbitals are used and the s orbital this means that there is p orbital which is not used.
- valence electrons left in the p-orbitals form Pi bonds.
hybridised orbitals form the sigma bonds .
How does sp hybridisation work?
- Promotion of one elctron from s orbital to p orbital
- hybridisation-where the orbitals mix to form hybrid orbitals with different energy
- sp= s+p
- therefore 50% s and 50% p so **the hybrid orbitals are inbetween p orbitals and 2s
- 2s is promoted to a higher energy level**
- so one p orbital is used and the s orbital this means that there are 2 p orbitals which is not used.
- valence electrons left in the p-orbitals form Pi bonds.
The hydbrised orbitals form sigma bonds.
How do sigma bonds form?
head on overlap of s orbitals or overlap hybrid orbitals
How do Pi bonds form?
Side on overlap of p orbitals
How strong is a C=C bond compared to a C-C bond?
Less than twice a strong because Pi bonds are weaker than sigma bonds.
What does conjugated mean?
Double bonds (or triple) seprated by a single bond or lone pairs adjacent to a double bond, which can be conjugated (delocalsied into a sysem)
NB some lone pairs are in hybridised orbitals so they can’t participate in resonance
it stabilises molecules as they always want a lower energy
What is the relationship between light and conjugated compounds?
The longer the conjugated system, the longer the wavelength of light absorbed
How does the colour of the conjugated compound occur?
The compound absorbs a certain frequency of visible light and appears as the complementary colour it absorbed.
What are the complementray colour pairings?
RED-GREEN
Orange-Blue
Yellow-Purple
What effect does conjugation have on structure?
An extended Pi bond is formed and e- are delocalised throughout extended Pi bonds.
Forcing the molecule to be planar
If there are many resonance structures which can be drawn for a compound then it is said to be…
highly resonance stabilised
How do you determine if a compound is aromatic?
It must:
1. Be cyclic
2. planar
3. COMPLETELY conjugated
4. have (4n+2)Pi electrons
If ANY ONE of the criteria for aromaticity is NOT satisfied then the compound is said to be…
Non-aromatic
If the compound satisfies the first 3 criteria for aromaticity but has 4n electrons then the compound is said to be…
anti-aromatic (destabilised)
What is the meaning of a conformation?
The different spatial arrangement of atoms or molecules that arises by the means of rotation about a c-c single bond.
What is a configuration?
The relative position of atoms or molecules can only be changed by cleaving and forming new bonds.
What is kinetics
The study of rates of reactions
What is thermodynamics?
A description of energy and how it is transferred between all systems
How do you measure reaction rates?
- Measuring concs. of products different times
what is rate of reaction?
the change in conc of a species per unit time OR rate of change in conc of a species
Why do reactions get faster with increase in temp
greater proportion of molecules have E> or equal to activation energy so more frequent successful collisions
