Organic Chem Test #2


Molecules that are not identical , but are mirror images

*Like a right hand is related to a left hand 


* results when a tetrahedral carbon is bonded to four dif substituents  


A molecule that is not identical to its mirror image


*Molecule with NO plane of symmetry

*Most commonly a Carbon connected to four different groups 




Optically active molecules that rotate to the LEFT


*Given a  (-) sign




Optically active molecules that rotate light to the RIGHT

*Given a (+) sign



Equation for Specific Rotation 



[a]d = a/l x c


a=observed degrees

l= pathlength (dm)

c=concentration (g/cm3)

Rank the following highest to lowest: 

-H, -Cl, -Br, -CH3, -CH2OH, -NH2, -B, -O

-Br, -Cl, -O, -NH2, -CH2OH, -CH3, -B, -H






Stereoisomers that are not mirror images

*Similar but not identical


* Have oppsosite configuration at some chirality centers but the same at others within the same chiral molecule 



Difference between Enantiomers and Diastereomers

enantiomers have opposite configurations at ALL chirality centers, diasteromers have opposite configurations at SOME (one or more) chirality centers but the same congfiguration at others.




Diasteriomers that differ by configuration at only one chirality center



Meso Compounds

ACHIRAL (non-chiral compound) that contain chirality centers



Racemic Mixture

*50/50 mixture of enantiomers



*Reacts with non-chiral molecules to form racemic mixture of enantiomeric products.





*Process of seperating racemic mixture


*employs chiral enantiopure resolving agents


*enantiopure reagents react with racemic mixture to form diastereomeric salts, which have diff physical properties and are seperated by crystallization



Constitutional Isomer


Compounds whose atoms are connected differently (same molecular formula)




compounds whose atoms are connected in the same order but with different arrangements in space

(enantomers, diastereomer [cis and trans]) 



Configurational Stereoisomer

configurational stereoisomer is a stereoisomer of a reference molecule that has the opposite configuration at a stereocenter (e.g., R- vs S- or E- vs Z-)



Prochiral Molecule

Molecule that can be converted from achiral to chiral  in a single chemical step (Changing a molecule with out affecting priority of other atoms)


*Have two faces Re (clockwise) Si (counterclock wise)


*Sp3 hybirdized prochiral atom can be Pro-S (replacement leads to a S chiral center) or Pro-R (replacement leads to R center)


What type of reaction is this?



Addition Reaction: 2 Reactants combine to form one product

What type of reaction is this?




Elimination Reaction: one reactant splits to form two products 


What type of reaction is this?



Substitution reaction: 2 reactants exchange substitients to form 2 new products

What type of reaction is this? 




Rearrangement reaction: single reactant rearranges its bonds. Mirgration of sigma bonds from 1->3 would be called [1,3]
Types of Addition reactions:


Hydrohalogenation of alkene



Hydrogenation of alkene



Addition of Nucleophile to Ketones and Aldehydes





Types of elimination reactons:

Dehydration of Alcohols

Dehydrohalogenation of Alkyl halides (haloalkanes



Types of Substitution reactions

Esterification of Carboxylic Acid


Hydrolysis of Ester



Homolytic Bond Cleavage

*symmetrical cleavage




*one bonding electron stays with each product






Heterolytic Bond cleavage

*unsymmetrical bond breaking




*two bonding electrons stay with one product





Radical Reactions

process that involves symmetrical bond-breaking and bond making 





a neutral chemical species taht contains an odd number of electrons and thus has a single, unpaired electron in one of its orbitals




Polar reactions 

* involves unsymmetrical bond breaking and bond making


*involve species that habe an even number ofelectrons 




Initiation step in methane chlorination




UV Light breaks weak CL-CL bond to give a few reactive chlorine radicals







Propagation step in methan chlorination

chloring radical collides with  methane molecule abstracting a hydrogen atom to give HCl and methyl radical (CH3)

* Methyl radical reacts furthar with Cl2 in second propagation step to give product chloromethane plus new chlorine radical, which repeats. 

*once initiated it becomes self sustaining / chain reaction






Termination of Methane chlorination


* When two radicals collide and combine to form a stable product. 

*Cycle is broke and chain is ended 


[Possible terminations]



What is a polar reaction?

* an electron pair is moved from electron-rich center(atom or bond) to electron-poor center.













Name 3 characteristics of a Nucleophile



* Negatively polarized electron rich atom


*form bond by donating pair of electrons to postively charges electron poor atom.


*Can be Neutral or Negative




Name 3 characteristics of an Electrophile



*positively polarized, electron poor atom


*forms bond by accepting pair of electrons from nucleophile


*Can be neutral or positvely charged



What is the equation for Keq (equilibrium constant)?


product concentrations multiplied together divided by the reactant concentrations mulitplied together with each concentrations raised to the power of its coefficient




Gibbs free energy change (ΔG) equation

 What is the favorable outcome?

* equal to the free energy of the products minus the free energy of the reactants:

* A negative value is more favorable

*energy is lost by the chemical sytem and released =exergonic (negative value)




ΔG = GproductsGreactants








enthalpy, ΔH

The energy exchange between bonds and the surrounding during this process is measured by enthalpy, ΔH (ΔH is primarily determined by the energy required to homolytically break a bond, also bond dissociation energy)



Heat of formation

The total change in enthalpy during bond breaking and bond forming reaction is called heat of formation.



Is heat absorbed or released during bond breaking/and formation

Bond breaking (heat absorbed)
Bond forming (heat release)



What is degree of unsaturation and how can you figure it out?

*# of rings and/or multiple bonds in molecules

*One degree = one double bond or one ring

*2 degree= two double bonds, or one double bond and a ring, or two rings, or one triple bond



Formula: DU= C-1/2(H+X-N)+1




Is Cis or Trans alkenes more stable? why?

Trans- alkenes are more stable than cis alkenes because cis alkenes have larger steric strain from the substituents. Therefore, alkenes always prefer the trans-siomers


Which bond is stronger Sp3-sp3 or Sp2-sp3?

Bond Strengths: sp2–sp3 carbons bond is stronger than sp3–sp3 carbons bond.





Bromine and Chlorine add rapidly to yield 1, 2 Dihalides


Chorine = cis or trans

Bromine=Always trans



1,2 disubstituted haloalcohol (X and OH)





What is this reaction?

Halohydrin reaction




*Alcohol adds to the most substituted Carbon


*Reacts with (Hg[Oac]2) followed by addition of sodium borohydride



What is this reaction?


*OH is added to the most substituted Carbon 





*nonmarkovnikov addition of OH group (adds to least substituted)


*Uses addition of BH3, in THF solvent, followed by addition of H2O2(hydrogen peroxide), and NaOH(sodium hydroxide)


What reaction is this?



*adds OH to least substituted carbon



*alkene converted to alkane 

*usually with (Pd/C) or platinum (Pt)

*Hydrogen added across the double bond




What reaction is this?



turns alkene to alkane with adding Hydrogen




*Decreases electron density on carbon by 

1. forming a carbon bond with O, N, or X(halogen)

2. Breaking a Carbon bond with Hydrogen 




*Increses electron density on carbon by
1.Forming carbon bond with Hydrogen

2.Breaking carbon bond with [O, N, and halogen] 




*add 2 hydroxyl  groups using  OsO4 & H2O2


What reaction is this?




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