Chapters 3, 4 Flashcards
What is an oxidizing agent?
An oxidizing agent is a molecule with two or more highly electronegative atoms directly bonded together.
ex: HN03, 03, HClO4
what position are most non-hydrogen groups favored in cyclohexane chairs? why?
In cyclohexane chair conformations, most non-hydrogen groups are most stable when in the EQUATORIAL position because there is minimal steric crowding at this position
What happens if a molecule is described as having unchanged stereoconfiguration ?
The molecule should be chiral and have sp3 hybridization
What are the properties for chair conformation ?
Chari conformation :
- allow all sp3 hybridized ring carbons to have a tetrahedral geometry.
What conditions should hydrogens be nucleophilic ?
nucleophilic hydrogens are actually strong bases.
-(nucleophilic usually means it has some degree of negative charge)
Which compounds undergo reduction with LIALH4? Which compounds don’t ?
Aldehydes, ketones and ester undergo reduction with LIALH4
-Acetals do NOT undergo reduction with LIALH4
what is an example of a strong electrophile (aka lewis acid)
FeBr3
What are examples of good nucleophiles ?
Iodide, carbons in Grignard reagents, and OH- (due to negative charge) are good nucleophiles
What are properties of lewis acids ?
A Lewis acid is a molecule that can ACCEPT a pair of nonbonding electrons. These molecules can be recognized easily because they always have a positive charge and/or an incomplete octet.
Ex; BF3
what type of compounds are usually in most stable chair configurations?
1,4 trans (that has both substituents on equatorial positions)
what are important properties of meso compounds ?
Meso compounds
- does not rotate plane polarized light
-internal plane of symmetry
-has a mirror image identical to it
what is the name of compound that rotates plane polarized light in clockwise direction ?
dextrorotatory (measured in positive degrees)
what is the name of compound that rotates plane polarized light in counterclockwise direction ?
Levorotatory (measured in negative degrees)
what is resolution of enantiomers?
When a racemic mixture is separated by chemical means, it leads to isolation of enantiomers.
what are the most stable conformations for compounds in Newman projections ?
most stable conformations :
single bonds in staggered conformation is more stable than eclipsed (due to steric repulsion)
-Conformations which put the largest substituents in an anti (180° apart) arrangement are more stable than those in a gauche (60° apart) arrangement.
How do you determine acidity of molecules?
look for electron withdrawing groups (like NO2, being stronger EWG and CN)
the closer the EWG is to carbonyl, the more acidic (as it stabilizes conjugate base through residence)
-also the more electronegative is an atom is and closer to carbonyl, the greater the inductive affect which increases acidity
what determines level of heat of combustion ?
Ring strain. Molecules with great ring strain will have highest energy, and hence higher level of heat of combustion
What are IUPAC rules for naming structures ?
When naming hydrocarbons, the longest linear carbon chain determines the root word
- Also, alcohols are a higher priority over halogens,
- substituents are placed in alphabetical order
What kind of chair confirmation is most stable?
a chair with no angle strain or torsional strain (eclipsing Hydrogens)
How do you determine stability of molecule if there is no resonance ?
the carbon substitution is used to determine the stability if there is no resonance
Since alkyl groups are electron donating, the least substituted carbanion is the most stable.
What is the formula for degree of unsaturation ? What is DOU for C14H12?
degree of unsaturation is given by the formula (2C + 2 - H)/2, where C is the number of carbon atoms and H is the number of hydrogen atoms.
ex: C14H12 contains (28 + 2 - 12)/2 = 9 units of unsaturation.
How do you determine basicity by electronegativity ?
The Less Electronegative atom is more basic
which structures have large amounts of ring and torsional strain ? Which have least amount?
Cyclopropane and cyclobutane have a great amount of ring strain
-cyclohexane has no ring strain (the best)
-cyclopentane has little ring strain
a
