OChem-Mcat review – Flashcards

*are monosubstituted ethylenes

*refers to the -CH₂ group as a substitute

*compounds that share only their molecular formula

*often have very different properties

*compounds that differ from each other only in the way that their atoms are oriented in space

*Includes:geometric isomers, enantiomers,diastereomers, and meso compounds

*compounds that differ in the position of substitutents attached to a double bond

*an object that is not superimposable upon its mirror image

(example right and left hand)

*Chiral objects that are nonsuperimposable mirror images

*refers to a pair of objects

*compounds that differ only by rotation about one or more single bonds

*(basically the same compound in a slightly different position)

*most stable conformation

*when two methyl groups are oriented 180? from each other

*min energy, min repulsive steric interactions

*occurs when the two methyl groups are 60? apart

*when the two methyl groups overlap

*highest energy state

1.) angle strain

2.)torsional strain

3.) nonbonded strain

*as MW increases so does MP, BP, and density

*at room temp, straight chains w/ C₁ to C₄ are gas

*at room temp, straight chains w/ C₅ to C₁₆ are liquid

*longer chains are wax or harder solid

*branching lowers BP, and MP

*Reaction of alkanes with molecular oxygen to form carbon dioxide, water, and heat

Rxn: C_nH_m + 5O₂ → 3CO₂ + 4H₂O + heat

*Break Down of a molecule by heat

*used to reduce the ave. MW of heavy oils and to increase the production of the more desirable volatile compounds

*If they have the same attacking atom, then the stronger the base = greater strength

Ex]

RO^->HO^->RCO₂^->ROH>H₂O

*in a protic solvent and when attacking atoms differ, large atoms tend to be stronger

CN^->I^->RO^->HO^->Br^->Cl^->F^-

*In aprotic solvents, strength is related to basicity

F^->Cl^->Br^->I^-

*best are those that are weak bases

--(these can accept an electron pair and dissociate to form a stable species)

ex] I^->Br^->Cl^->F^-

*Unimolecular nucleophilic substitutions

*rate is dependent upon only one species, formation of Cation

~*Mech*~

Step 1.) dissociation of molecule to form carbocation

Step 2.) Attack of Nucleophil on Carbocation

*Highly substituted cations are more stable

 ~~**Favored in polar protic solvents

*involves a nucleophil pushing its way into a compound while simultaneously displacing the leaving group

*rate is determined upon substrate and nucleophile

~*Favored in polar aprotic solvents

=.5 (2n+2-m)

*for the compound C_nH_m

*MP and BP increase w/ MW

*Trans- have higher MP (due to symmetry) and Lower BP (due to less polarity) than Cis

*Two-step process

*rate is dependent on substrate

*Elimination of a leaving group, then proton is removed by a base forming a double bond

~*Favored Highly polar solvents, highly branched carbon chains, good leaving groups and weak nucleophiles in low concentrations

*Occurs in 1 step.

*rate is determined by both substrate and the base

*strong base removes proton while halide leaves forming double bond

*used to determine aromaticity

*4n + 2 pi electrons = # carbons

~* Solve equation for n, if n is a nonnegative integer compound is aromatic

*Similar to other hydrocarbons however the Delocalization stabilizes the molecule making it unreactive

*Higher BP (due to H-bonding)

;

*DO NOT UNDERGO H- BONDING

*Low BP (compared to Alcohols)

*slightly polar

*often used as solvent (are unreactive to most organic reagents)

*Higher BP than alkanes due polar group (but still lower than alcohols)

*Are polar

*higher BP than alcohols and increase w MW

*Acidity;is due to carboxylate anion

*BP is b/w alkanes and alcohols

*are basic and readily accept protons

*transfer of a dissolved compound from one solvent into another in which it is more soluble

*impurities are left behind in the first solvent

*Both solvent are immisible

*used to isolate a solid from a liquid

;

*process in which impure crystals are dissolved in a minimun amount of hot solvent. Once cooled the crystals reform leaving impurities in the solvent

*Occurs when a heated solid turns directly into a gas w/o an intervening liquid stage

*most impurities will not sublime easily

;

*The separation of one liquid from another through vaporization and condensation

1)simple, 2)Vacuum, 3) fractional