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Orgo 20
Organic Chemister, Chapt 20
| Question | Answer |
|---|---|
| Aliphatic acids have an ____ group bonded to -COOH. Aromatic acids have an _____ group. _______ are long-chain aliphatic acids. | Alkyl group; aryl group; Fatty-acids |
| Bond angles of the carboxyl group are close to _____. The O-H is eclipsed with the C=O to get overlap of ___ orbital with orbital of ____ on oxygen. | 120 degrees; overlap of PI orbital with LONE PAIR on oxygen |
| Carboxylic acids have ____ BP than similar alcohol due to _______ formation. | Higher BP; dimer formation |
| _____ acids with more than ___ carbons are solids at room temperature. ______ lower the melting point. | Aliphatic (no aromatic ring); >8 carbons; double bonds lower MP |
| Water solubility of carboxylic acids _____ with the length of the carbon chain. Up to ___ carbons, acid is miscible in water. However, it is more soluble in _____, and also in chloroform b/c it dissolves as a ____. | decreases; 4; alcohol; dimer |
| Carboxylic acids are ____ acids. The values of pKa for most aliphatic and aromatic carboxylic acids fall within the range of __-__. | weak; 4-5. |
| What are the two factors that account for the greater acidity of carboxylic acids relative to alcohols? | The electron-withdrawing inductive effect of the adjacent carbonyl group weakens the O-H bond, and the carboxylate anion is stabilized by resonance. |
| Electron-withdrawing substituents near the carboxyl group _____ the acidity through their _____ effect. Multiple substitution of electron-withdrawing groups _____ acidity. | Increase; inductive; further increases |
| The ______ effect of an electron-withdrawing substituent falls of rapidly with its _____ distance from the carboxyl group. | inductive; increased |
| Carboxylic acids (whether soluble or insoluble in water), react with NaOH, KOH and other strong bases to give _________. They also form these when reacted with ______. | Water-soluble salts; ammonia and simple amines |
| COOH + NaOH (or KOH) --> | Salt + Water |
| Carboxylic acids reacts with sodium bicarbonate and sodium carbonate to form ________ and _______ (which breaks down to _______ and _______). | water-soluble salts; carbonic acid which breaks down to CO2 and H2O |
| Acids salts are usually ____ with no odor. Carboxylic salts of (___, ___, ___ and ___) are soluble in water. | solids; K+, Na+, Li+, NH4+ |
| _____ is the soluble sodium salt of a long chain fatty acid. Salts can be formed by the reaction of COOH with ____, releasing ____. | Soap; NaHCO3 releasing CO2 |
| The carboxyl group gives two characteristic absorptions. _____-______ is associated with the stretching vibration of the C=O group. ____-____ is associated with the stretching of the O-H group. | 1700-1725 for C=O; 2400-3400 for O-H |
| Hydrogens on the alpha carbon to a carboxyl group appear in the range ___-___ in H-NMR. The hydrogen of the carboxyl group appears in the range ___-___. | 2.0-2.5 alpha carbon hydrogens; 10-13 hydrogen of carboxyl group |
| In C-NMR, the carboxyl carbon appears in the range ____-___. | 160-180 |
| The most common fragmentation patterns for a carboxyl group in Mass Spec is the ___-cleavage of the carboxyl group to give the ion _____ of m/z ____, as well as the _______ rearrangement. | alpha; [Co2H]+ of m/z 45; McLafferty Rearrangement |
| Cleavage of an alkene with hot KMnO4 produces a ______ if there is a _____ on the double-bonded carbon. | Carboxylic acid; hydrogen |
| Alkyl benzene is oxidized to _____ by hot KMnO4 or hot chromic acid. | benzoic acid |
| Grinard Reagent (R-MgBr) + CO2 -> _____ | carboxylate salt (R-COOH) |
| Basic or acidic ______ of a nitrile produces a ______. | hyrolysis; carboxylic acid |
| R-Br + NaCN-> R-___ + H+/H2O -> R-___ | R-CN -> R-COOH |
| What is the reactivity trend for the carboxylic acid derivatives undergoing Nucleophilic Acyl Substitution? | (Most Reactive) Acyl Chloride > Anhydride > Ester > Amide (Least Reactive) |
| Carboxylic acid derivatives interconvert via __________. It is only feasible when a ___ stabilized carbonyl is converted to a ____ stabilized one (____ reactive to ____ reactive) | nucleophilic acyl substitution; less stable converted to more stable (more reactive to less reactive) |
| Carboxylic Acid + Alcohol -> ____ + ____ | ester + water |
| In the Fischer Esterfication (condensation), it is ___-catalyzed for a weak nucleophile. All steps are ______. The reaction reaches _____. | acid; reversible; equilibrium |
| The first step of the Fischer Mechanism is ____ of carbonyl of carboxylic acid, and attack of ____. This is followed by protonation of ____ and loss of ____. The final result is an _____. | protonation of carbonyl; attack by alcohol; protonation of -OH, loss of H2O. Final result is an Ester. |
| In the esterfication of a carboxylic acid, the oxygen of the ______ is incorporated. | Alcohol |
| CH2N2 (diazomethane) reacts with COOH to produce ______. These are very toxic and explosive, and dissolve in _____. | Methyl Esters; dissolve in ether |
| COOH + CH2N2 -> ______ | COOCH3 + N2 |
| The mechanism for diazomethane with carboxylic acid begins with a _____ to Diazomethane, producing a _____. This is followed by nucleophilic attack by _____ on the ____ group of the _____, producing _____ and _____. | proton transfer to Diazomethane; produces methyldiazonium salt and carboxylate ion; nucleophilic attack by the carboxylate ion on the methyl group of the salt. Produces an methylester and N2 gas |
| Carboxylic Acid + Amines -> _____ | Amide + H2O |
| In the synthesis of amides, ____ removes a proton from the ________ to form a salt. _____ drives off steam and forms the amide. | an Amine (base) removes proton from Carboxylic acid. Heating the salt above 100C |
| Using a strong reducing agent like LiAlH4 reduces carboxylic acids to _____. | Primary Alcohol |
| Borane (BH3 in THF) reduces carboxylic acid to ________, but does not reduce ______. | reduces COOH to alcohol; does NOT reduce ketones! |
| It is difficult to stop reduction reactions at aldehydes. To do so, use a more reactive form of the acid (such as ______) and a ____ reducing agent such as LiAl[OC(CH3)3]3H | use reactive form such as an Acid Chloride; , WEAKER reducing agent |
| COOH + 2R-Li/H2O -> _____ | ketone |
| To get a ketone, you must react _____ of an organolithium reagent with a carboxylic acid. | 2 equivalents ( COOH + 2R-Li -> ketone) |
| To synthesize _________ (an activated form of COOH which is a good leaving group), use thionyl chloride or oxalyl chloride with the carboxylic acid. These give additional produces of ____ + ____ + _____. | acid chlorides; HCl + CO2 + CO |
| Acid Chloride + Alcohol -> ____ | Esters in good yield |
| The mechanism of acid chloride to ester is ________ of alcohol to the _______ as _____ leaves. Then _______. | nucleophilic addition of alcohol to the carbonyl as a chloride ion leaves. Then deprotonation. This gives an ester and HCl |
| Acid Chloride + Ammonia or Amine -> _____ | amide |
| To make an amide, an _____ is reacted with ammonia or amine. A ____ is added to remove ____ by-product. | Acid chloride; base is added to remove HCl by-product |
Created by:
jgold37