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OChem-Mcat review
n/a
49
Chemistry
Graduate
06/09/2011

Additional Chemistry Flashcards

 


 

Cards

Term
Vinyl-
Definition

*are monosubstituted ethylenes

 

Term
allyl-
Definition
*are propylenes substituted at the C-3 position
Term
Methylene-
Definition

*refers to the -CH2 group as a substitute

 

Term
isomers
Definition
*chemical compounds that have the same molecular formula but differ in structure
Term
Structural Isomers
Definition

*compounds that share only their molecular formula

*often have very different properties

Term
Stereoisomers
Definition

*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

Term
Geometric Isomers
Definition

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

 

Term
Chirality
Definition

*an object that is not superimposable upon its mirror image

(example right and left hand)

Term
Enantiomers
Definition

*Chiral objects that are nonsuperimposable mirror images

*refers to a pair of objects

Term
relative configuration
Definition
*of a chiral molecule is its configuration in relation to another chiral molecule
Term
absolute configuration
Definition
*of a chiral molecule describes the spatial arrangement of these atoms or groups
Term
Diastereomers
Definition
*stereoisomers that are not mirror images
Term
Meso compound
Definition
*contains a plane of symmetry, and is not optically active
Term
Conformational isomers
Definition

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

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

Term

Staggered (anti) conformation

 

Definition

*most stable conformation

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

*min energy, min repulsive steric interactions

 

 

Term

Gauche conformation

(staggered)

Definition

*occurs when the two methyl groups are 60º apart

Term
Eclipsed conformation
Definition
the two methly groups are 120º apart and overlap with the H atoms on the adjacent carbon
Term
Totally eclipsed
Definition

*when the two methyl groups overlap

*highest energy state

Term
What type of strains do cycloalkanes have?
Definition

1.) angle strain

2.)torsional strain

3.) nonbonded strain

Term
Physical properties of alkanes
Definition

*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

Term
Combustion
Definition

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

 

Rxn: CnHm + 5O2 → 3CO2 + 4H2O + heat

Term

Pyrolysis

(AKA Cracking)

Definition

*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

Term
What is a nucleophile
Definition
Nucleus loving
Term
How does basicity effect a nucleophile?
Definition

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

Ex]

RO->HO->RCO2->ROH>H2O

Term
How does Size and polarizablity effect nucleophiles
Definition

*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-

Term
Leaving group
Definition

*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-

Term
SN1 reactions
Definition

*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

Term
SN2 reactions
Definition

*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

Term

what effects whether a reaction will be

SN1 or SN2 ?

Definition
*Sterics, nucleophil strength, leaving group ability, reaction conditions, and solvent effects.
Term

Degree of Unsaturation

(The number (N) of double bonds)

 

Definition

=.5 (2n+2-m)

*for the compound CnHm

Term
Physical properties of Alkenes
Definition

*MP and BP increase w/ MW

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

 

Term
Unimolecular elimination (E1)
Definition

*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

 

Term

Bimolecular Elimination (E2)

 

Definition

*Occurs in 1 step.

*rate is determined by both substrate and the base

*strong base removes proton while halide leaves forming double bond

Term
Huckel's rule
Definition

*used to determine aromaticity

*4n + 2 pi electrons = # carbons

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

Term
Meta-
Definition
*1,3 disubstituted compounds
Term
Ortho-
Definition
*1,2 disubstituted compounds
Term
Para-
Definition
*1,4 disubstituted compounds
Term
Physical properties of Aromatic Compounds
Definition

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

Term
Physical properties of Alcohols
Definition

*Higher BP (due to H-bonding)

 

Term
Physical Properties of Ethers
Definition

*DO NOT UNDERGO H- BONDING

*Low BP (compared to Alcohols)

*slightly polar

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

Term
Physical properties of Aldehydes and ketones
Definition

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

Term
Physical properties of carboxylic acids
Definition

*Are polar

*higher BP than alcohols and increase w MW

*Acidity is due to carboxylate anion

Term
Properties of amines
Definition

*BP is b/w alkanes and alcohols

*are basic and readily accept protons

Term
Extraction
Definition

*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

Term
Filtration
Definition

*used to isolate a solid from a liquid

 

Term
Recrystallization
Definition

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

Term
Sublimation
Definition

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

*most impurities will not sublime easily

 

Term
Distillation
Definition

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

1)simple, 2)Vacuum, 3) fractional

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