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29 Cards in this Set
- Front
- Back
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As far as the number of p orbitals, what is good way to interpret sp^3?
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All 3 of the p orbitals have been hybridized; none remain
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As far as the number of p orbitals, what is a good way to interpret sp^2?
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2 of the p orbitals have been hybridized; only 1 remains.
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As far as the number of p orbitals, what is a good way to interpret sp?
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1 of the p orbitals ahve been hybridized; 2 remain
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When a carbonyl bond breaks, (C=O), what usually happens to the electrons?
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Electrons from teh pie bond end up as negative chage on the oxygen
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What does the cyanide attack on hydrides usually occur in the presence of and why?
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Usually occurs in the presence of acids, because the Cn- attacks the C=O crotch ~ O becomes negative and attracts H+
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Show how dissolving a cyanohydrin in water can give back the aldehyde or keton you started with.
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B-1
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What is more favorable: ketone cyanohydrins or aldehyde cyanohydrins?
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Aldehyde cyanohydrins
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Why are ketone cyanohydrins less favorable than aldehyde cyanohydrins?
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Aldehyde cyanohydrins are more favorable than keton cyanohydrins, because of the size of the groups attached to the carbonyl carbon atom. Aldehyde central carbon has less steric hinderance - one of the bonds coming off is to an H, (which is very small), making the reduction in angle less of a problem than than with a larger group coming off in ketone.
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What is the Burgi-Dunitz trajectory?
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Nucleophiles attack the plane of the carbonyl group at about 107 degrees to the C=O bond.
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In terms of nucleophile attack angle, what is steric hinderance?
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Portions of the molecule that get in the way of the Burgi-Dunitz trajectory
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Does nucleophilc attack by H- ever happen?
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No
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Why doesn't nucleophilic attack by H- ever happen?
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H- one s-orbital is too small to act as nucleophilically.
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What happens instead of H- acting as a nucleophile? Draw an example.
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H- acts as a base, pulling off another H from H-X, leaving X-, which then acts as the nucleophile.
-or- Hydrogen atom is trasnferred with an attached pair of electrons'. which can still be regarded as a"'hydride transfer. Example: B-2 |
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What is the difference between an aldehyde and a ketone?
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Both have C=O
Aldehydes have an H coming off of the central C, whereas ketones have R coming off of the central C. |
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Draw the reaction of lithium aluminum hydride to show why it reacts violently and dangerously with water in an exothermic reaction.
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B-3
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Why are organometallic reagents strong nucleophiles?
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They are highly polarized toward the carbon.
Ex.: Li-C and Mg-C |
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Can water be present during the reaction of organometallic reagents with carbonyls?
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No, because water destroys the organometallics before they have a chance to react with the carbonyls.
Ex. B-4 |
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What are Grignard reagents?
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Organomagnesium reagents that are among the most important ways of making carbon-carbon bonds.
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Draw an example of a reaction involving a Grignard reagent.
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Ex. B-5
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Why does an aqueous solution of formaldehyde contain essentially no CH2O? Draw the reaction.
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It is completely hydrated
B-6 |
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As the equibrium constant gets larger, does the reaction shift more to the left or to the right?
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The larger the equilibrium constant, the more the equilibrium is to the right.
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Do cyclopropanones want a larger or smaller bond angle? Why?
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Cyclopropanones prefer a smaller bond angle, because in the cyclopropanone, central carbon is sp^2, so it wants 120 degrees, whereas in cyclopropanone hydrate, the central carbon is sp^3, so it only wants 109 degrees. therefore, when cyclopropanone and cyclopropanone hydrate both get 60 degrees, the cyclopropanone hydrate is happier, becuase there is less of a difference from its ideal bond angle.
Drawn: B-7 |
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WHa tis a hemiacetal and how is it formed?
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Hemiacetal is "halfway to an acetal;" formed by an alcohol acting on a carbonyl
Ex.: B-8 |
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Show an example of an intramolecular reaction that forms a hemiacetyl.
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Ex.: B-9
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In the reaction in B-10, what acts as the catalyst?
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Ethanol, (EtOH)
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How does an acid catalyst work for carbonyl groups?
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Make the carbonyl group more electrophilic.
Illustrated in B-11. |
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How does a base catalyst work for carbonyl groups?
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Make the nucleophile more nucleophilic.
Illustrate in B-11. |
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Draw a reaction involving sodium bisulfite and a ketone.
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B-12
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How are sodium bisulfite compounds made?
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Made by mixing the ladehyde or ketone with saturated aqueous sodium bisulfit in an ice bath, shaking, and crystallizing.
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