Organic Chem Test #2 – Flashcards
Unlock all answers in this set
Unlock answersEnantiomer |
Molecules that are not identical , but are mirror images
* results when a tetrahedral carbon is bonded to four dif substituents |
Chiral |
A molecule that is not identical to its mirror image
*Molecule with NO plane of symmetry |
Levorotatory |
Optically active molecules that rotate to the LEFT
*Given a (-) sign |
Dextrorotatory |
| 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 |
Diastereomer |
Stereoisomers that are not mirror images
* 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. |
Epimer |
| 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.
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Resolution |
*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) |
Stereoisomer |
| compounds whose atoms are connected in the same order but with different arrangements in space (enantomers, diastereomer [cis and trans]) |
Configurational Stereoisomer |
| A 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?
[image] |
| Addition Reaction: 2 Reactants combine to form one product |
What type of reaction is this?
[image] |
| Elimination Reaction: one reactant splits to form two products |
What type of reaction is this?
[image] |
| Substitution reaction: 2 reactants exchange substitients to form 2 new products |
What type of reaction is this?
[image] |
| 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
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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
*Radical
*one bonding electron stays with each product
[image] |
Heterolytic Bond cleavage |
*unsymmetrical bond breaking
*polar
*two bonding electrons stay with one product
[image] |
Radical Reactions |
| process that involves symmetrical bond-breaking and bond making |
Radical |
| 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
[image]
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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
[image] |
Termination of Methane chlorination |
* When two radicals collide and combine to form a stable product. *Cycle is broke and chain is ended [image] [Possible terminations] |
What is a polar reaction? |
* an electron pair is moved from electron-rich center(atom or bond) to electron-poor center.
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Name 3 characteristics of a Nucleophile |
NUCLEUS LOVING
* Negatively polarized electron rich atom
*form bond by donating pair of electrons to postively charges electron poor atom.
*Can be Neutral or Negative
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Name 3 characteristics of an Electrophile |
ELECTRON LOVING
*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
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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 = Gproducts - Greactants
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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. |
Halogenation |
Bromine and Chlorine add rapidly to yield 1, 2 Dihalides
Chorine = cis or trans Bromine=Always trans |
Halohydrin |
1,2 disubstituted haloalcohol (X and OH)
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[image]
What is this reaction? |
| Halohydrin reaction |
Oxymercuration-demercuration |
*Alcohol adds to the most substituted Carbon
*Reacts with (Hg[Oac]2) followed by addition of sodium borohydride
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[image] What is this reaction? |
| Oxymercuration-demercuration *OH is added to the most substituted Carbon |
Hydroboration |
*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) |
[image] What reaction is this? |
Hydroboration
*adds OH to least substituted carbon |
Hydrogenation |
*alkene converted to alkane *usually with (Pd/C) or platinum (Pt) *Hydrogen added across the double bond
|
[image]
What reaction is this? |
Hydrogenation
turns alkene to alkane with adding Hydrogen |
Oxidation |
*Decreases electron density on carbon by 2. Breaking a Carbon bond with Hydrogen |
Reduction |
*Increses electron density on carbon by 2.Breaking carbon bond with [O, N, and halogen] |
Dihydroxylation |
| *add 2 hydroxyl groups using OsO4 & H2O2 |
[image] What reaction is this? |
Dihydroxylation |
