Milkteeth

Extractionista
10+ Year Member
Jul 15, 2008
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Dental Student
Ok...
someone please help me out in knowing the general rules and/ or trends for identifying:
1. Acidity
2. Basicity
3. Boiling point
4. Melting point of a compound, please.

For example, The more substituted a compound is, the higher boiling point it will have, etc

Thanks!
 
Jun 14, 2009
156
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Status
Pre-Dental
from highest to lowest for acidity... carboxy acid attached to benzene then carboxy acids then phenols then alcohols then alkynes then akenes then alkanes:D:cool:
 
Jun 14, 2009
156
0
Status
Pre-Dental
u can have groups that increase basicity which include nh2 ch3 c2h5
u can have groups that increase acidity cooh no2 cn so3h
 
Jul 16, 2009
11
0
Status
Dental Student
Ok...
someone please help me out in knowing the general rules and/ or trends for identifying:
1. Acidity
2. Basicity
3. Boiling point
4. Melting point of a compound, please.

For example, The more substituted a compound is, the higher boiling point it will have, etc

Thanks!
groups that increase basicity: DEstabilize the lone e pair (usually 2 donating groups)
groups that increase acidity: electron withdrawing groups (groups that can STABILIZE the resulting neg. charge after losing a proton) eg: conjugated systems, highly electronegative atoms, etc

Boiling point: when external pressure = vapor pressure

higher MW = higher BP,
more branching = lower BP, MP (london dispersion forces weaker because molecules are "stacked" more loosely due to branching)
hydrogen bonding = higher BP, MP (remember, only NH, OH, and FH are capable of H bonding)
cis/trans: cis isomers will have a higher BP than trans isomers because cis isomers are more polar. Trans isomers will have a higher melting point because their conformation allows them to be "stacked" more tightly, their symmetry generally allows better packing in the solid state

ionic compounds will have a higher melting point than covalent compounds due to ionic interactions


Hope tihs was helpful, feel free to correct me if I got something wrong!
 
Jul 16, 2009
11
0
Status
Dental Student
Also: compounds with more "s" character tend to be more acidic than compounds with less "s" character

example:
ethane (sp3) < ethene(sp2) < ethyne(2p3)
increasing acidity-->
 
OP
M

Milkteeth

Extractionista
10+ Year Member
Jul 15, 2008
42
0
Status
Dental Student
Thnak u so much guys this was very helpful! MissNo - very specific thanks a mil!
Sometimes I get so confused. One minute I know it n then a question or two totally throws me off.