OCHEM Fundamentals Flashcards
Principles of reactivity
Steric hindrance
Reactivity decreases because of protecting groups, such as acetals, which block off the reactive center.
Principles of reactivity
Induction
Reactivity increases with more electronegative groups because it changes the distribution of charge and the distribution of resonance forms.
Principles of reactivity
Conjugation
Reactivity decreases with alternating single and double/triple bonds due to stabilization of resonance forms.
Principles of reactivity
Ring strain
Smaller bond angles in a ring increase torsional strain, therefore increasing reactivity.
Resonance forms
Resonance forms are a way to understand electron densities on a molecule with π bonds (double or triple bonds) next to a p orbital or lone pair).
The “true form” of a molecule is a weighted hybrid of the different resonance forms.
Resonance
Resonance form principles
A way to determine which resonance forms are more significant and stable. These principles are guided by rule of least charges, octet rule, stabilization of negative charges, principle of hybridization
Resonance
Rule of least charges
The fewer charged atoms in a resonance form, the more stable it is.
Resonance
Octet principle
Resonance forms with full octets are more stable. Oxygen and nitrogen should nearly always have a full octet.
Resonance
Stabilization of negative charges
Stability of negative charges is the inverse of basicity. For example, as electronegativity increases across a row of the periodic table, basicity decreases and stability increases.
Resonance
Principle of hybridization
Negative charges are more stable on atoms with greater proportion of s-character (for example sp, 50% s character, is more stable than sp3, 25% s character)
Positive charges are more stable on atoms with lower proportion of s-character.
Redox agents
Strong oxidizing agents are Jones reagent, or metallic oxides like K2CrO7, KMnO4 which will oxidize alcohols “all the way” to carboxylic acids
Weak oxidizing agents like PCC will oxidize a primary alcohol “one step away” to an aldehyde
The mild oxidizing agent Tollens reagent will selectively oxidize aldehydes but not ketones or alcohols
Oxidizing agents
Redox agents
Reducing agents
The strongest reducing agents are hydrides like LiAlH4
The hydride NaBH4 is slightly weaker than LiAlH4. It will reduce aldehydes and ketones to alcohols but will not be able to reduce esters, carboxylic acids, amides
Nomenclature
Hydrocarbons
Nomenclature
Alcohols
Nomenclature
Amines
Nomenclature
Aldehydes
Nomenclature
Ketones
Nomenclature
Carboxylic Acids
Nomenclature
Ester
Nomenclature
Amide
Redox
How to reduce carboxylic acids, aldehydes, and ketones to alkanes
