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CHM 2110
Exam III
| Term | Definition |
|---|---|
| α carbons are directly bonded to ____. | a halogen |
| β carbons are directly bonded to ____. | α carbons |
| What is an example of a methyl alkyl halide? | an alkyl halide that has its α carbon bonded to a halogen and NO other carbons |
| What is an example of a primary alkyl halide? | an alkyl halide that has its α carbon bonded to a halogen and ONE other carbon |
| What is an example of a secondary alkyl halide? | an alkyl halide that has its α carbon bonded to a halogen and TWO other carbons |
| What is an example of a tertiary alkyl halide? | an alkyl halide that has its α carbon bonded to a halogen and THREE other carbons |
| How does the addition of the halogen to an alkene (formation of alkyl halide) affect boiling point? Why does is do this? | It increases the boiling point by the addition of polar bonding between the α carbon and halogen. |
| Electrophiles seek or want ____. | Electrons |
| Nucleophiles seek or want ____. | Protons |
| Substitution reactions depend on substrate structure, leaving group, nucleophiles, and competition with what other mechanism? | elimination |
| What rate law does SN2 reactions undergo? | rate=k[substrate][nucleophile] |
| In SN2 reactions, where will the nucleophile be after kicking out the leaving group? | in the opposite direction as the leaving group |
| When drawing the transition states of ANY reaction, what must you include if you draw two (or more) dashed bonds? | "bonds forming" and "bonds breaking" |
| Generally, the more steric a molecule has, the ____ the rate of reactions it undergoes will be. | slower |
| According to Arrhenius equation, if you have more steric, you will have a higher activation energy barrier and a ____ k constant. | lower |
| What is Arrhenius equation? | k=Ae^(-Ea/RT) |
| Which is a better nucleophile: a partial charged molecule (water) or a full charged molecule (OH-)? | full charged molecule |
| Why are larger atoms generally better nucleophiles? | larger atoms can accommodate more charge better than smaller atoms |
| The ____ a base is, the better it is as a leaving group. | weaker |
| How many steps are in SN2 and E2 reactions? | one |
| A π bond exists between two WHAT hybridized carbon atoms? | sp2 |
| During elimination reactions, what carbon does the halogen leave from? | α carbons |
| During elimination reactions, what carbon does the proton leave from? | β carbons |
| After sp2 hybridization, what is orbital is left? | 2pz orbital |
| To figure out what kinds of product will be produced during a reaction, Dr. Fossum says to look at two things: sterics and ____. | electronics: electronegativity and resonance |
| What types of alkyl halides are unlikely or won't undergo E1 reactions at all? | methyl and primary |
| Generally, the ____ the molecule, the more likely it is to undergo E1 reactions. | bulkier |
| What is the Zaitsev Rule? | smaller bases lean towards the production of internal π bonds |
| What is the Hoffman Rule? | larger bases lean towards the production of external π bonds |
| Why are internal π bonds more stable than external π bonds? | internal bonds have more bulk around the π bond, making it more stable |
| Why is the trans stereochemistry of an alkene more stable than cis stereochemistry? | cis stereochemistry leads to an eclipsed Newman projection, making it less stable |
| What is an exception to trans stereochemistry of an alkene being more stable than cis stereochemistry? | cycloalkenes form cis π bonds |
| SN1 and E1 reactions consist of how many steps? | two |
| The production of what INTERMEDIATE automatically tells you that SN1 or E1 is occurring? | carbocation |
| What rate law does SN1 and E1 reactions follow? | rate=k[substrate] |
| What is the first step of SN1 and E1 reactions? | the leaving groups leaves |
| A carbocation has what molecular GEOMETRY? | trigonal planar |
| A carbocation has what hybridization? | sp2 hybridization |
| During elimination reactions, the β carbon with the ____ sterics will most likely give up the proton. | most |
| What does regiochemistry tell us about in a reaction? | It tells us what REGIONS chemistry will occur at |
| Why does the SN1 reaction produce racemic mixtures? | the nucleophile can attack from either of the two empty p orbitals of the original planar carbocation |
| What is a racemic mixture? | a product of SN1 reactions; a combination of the nucleophile that attacked from both empty p orbitals |
| If you cannot assign R and S stereochemistry on a molecule containing a π bond, what two other stereochemistries can be used? | entgegen (E) and zusammen (Z) |
| What is entgegen (E) stereochemistry? | the highest priority groups on each of the sp2 carbons are on opposite side |
| What is zusammen (Z) stereochemistry? | the highest priority groups on each of the sp2 carbons are on the same side |
| Racemic mixtures are: enantiomers, diasteriomers, constitutional isomers. | enantiomers |
| What is the pKa of HBr? Is Br- a strong or weak base? | -9; weak |
| What is the pKa of HCl? Is Cl- a strong or weak base? | -7; weak |
| What is the pKa of HI? Is I- a strong or weak base? | -10; very weak |
| Why can't methyl and primary alkyl halides undergo SN1 or E1 reactions? | they do not form stable carbocations due to little to no steric hinderance |
| Strong bases generally lean towards substitution or elimination reactions? | elimination |
| Methyl alkyl halides only undergo what kind of reaction? | SN2 |
| For primary, secondary, and tertiary alkyl halides, if you have a WEAK nucleophile but a STRONG base, what reaction will occur? Why? | E2; SN2 reactions are not observed |
| Nucleophiles bond to ____ atoms (typically). | carbon |
| Bases bond to ____ atoms. | hydrogen |
| With a strong nucleophile and strong base, such as NaOH, what will be the reaction(s) for a primary alkyl halide? | major: SN2; minor: E2 |
| With a strong nucleophile and strong base, such as NaOH, what will be the reaction(s) for a secondary alkyl halide? | major: E2; minor: SN2 |
| With a strong nucleophile and strong base, such as NaOH, what will be the reaction(s) for a tertiary alkyl halide? | E2 only |
| With a strong nucleophile and strong base, if you want a primary alkyl halide to undergo E2 reaction, what kind of reagent should you have: non-bulky or bulky? | bulky |
| With a strong nucleophile, WEAK base, wha kind of products dominate? Why? | substitution; elimination reactions don't occur fast enough with weak bases |
| EtONa is a ____ nucleophile and a ____ base. | strong; strong |
| OK is a ____ base and it's bulky. | strong |
| NaCl is a ____ nucleophile and a weak base. | strong |
| OH signals on an IR spectrum can be classified by a broad signal around what wavenumber? | 3200-3600 |
| Sp2 C-H bonds on IR spectrum can be classified by a C-H signal around what wavenumber? | 3100 |
| In an H+ NMR spectrum, if a triplet is directly bonded to an oxygen, will it most likely be closer to 1ppm (downstream) or 4ppm (upstream)? Why? | 4ppm (upstream); The oxygen will deshield the triplet, making it more upstream |
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