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Org Chem Ch.19
Carboxylic Acids and the Acidity of the O-H bond
| Question | Answer |
|---|---|
| Carboxylic acids are organic compounds contain a ________ group | carboxy (COOH) |
| Because the oxygen is more electronegative than either carbon or hydrogen, the C-O and O-H bonds are _______ | polar |
| IUPAC: how doe you name a carboxylic acid if the COOH is bonded to a chain of carbons? | find longest chain containing COOH, and change the -e ending of the parent alkane to the suffic -oic acid |
| IUPAC: how do you name a carboxylic acid if the COOH is bonded to a ring? | add the words carboxylic acid |
| IUPAC: When numbering the chain, what number should you give the COOH carbon atom? | C1 |
| Common names: a common name is formed by using a common parent name followed by the suffix... | -ic acid |
| Common names: How are carbons named in common names? | Greek symbols are used, beginning with the carbon adjacent to the COOH (alpha carbon, then beta, gamma, delta etc) |
| Common names: The last carbon in the chain is sometimes called the ______ carbon | omega |
| Common name: parent name for 1 carbon (COOH) | form- (formic acid) |
| Common name: parent name for 2 carbons | acet- (acetic acid) |
| Common name: parent name for 3 carbons | propion- (propionic acid) |
| Common name: parent name for 4 carbons | butyr- (butyric acid) |
| Common name: parent name for 5 carbons | valer- (valeric acid) |
| Common name: parent name for 6 carbons | capro- (caproic acid) |
| Common name: parent name for benzene | benzo- (benzoic acid) |
| IUPAC: How are diacids named? | adding the suffix -dioic acid to the name of the parent alkane |
| IUPAC: How do you name the metal salt of a carboxylate anion? | change the -ic acid ending of the carboxylic acid to the suffix -ate. Then its [The name of the metal cation + parent + suffix] |
| Carboxylic acids exhibit ________-________ interactions because they have polar C-O and O-H bonds | dipole-dipole interactions |
| Carboxylic acids exhibit intermolecular _______ __________ because they possess a hydrogen atom bonded to an electronegatice oxygen atom | hydrogen bonding |
| carboxylic acids often exist as _______, held together by two intermolecular hydrogen bonds between the carbonyl oxygen atom of one molecule and the OH hydrogen atom of anothe rmolecule | dimers |
| as the strength of the intermolecular forces increase, the boiling point and melting point _________ | increase |
| carboxylic acids have a _________ boiling points and melting point than other compounds of comparable MW | higher |
| boiling point coincides with _______ | polarity (lease polar will have lowest bp and most polar with have highest bp |
| carboxylic acids are ________ in organic solvents regardless of size | soluble |
| Explain the solubility of carboxylic acids in water | carboxylic acids having 5 or less C's are water soluble, carboxylic acids have more than 5 C's are insoluble in water |
| Why can't larger carboxylic acids dissolve in water? | the nonpolar alkyl portion is too large to dissolve in the polar H2O solvent |
| Why can smaller carboxylic acids dissolve in water? | they can hydrogen bond with H2O |
| What do larger carboxylic acids (fatty acids) dissolve in? | non-polar, fat-like environment |
| Preparation of carboxylic acids: reactions that produce a particular functional group are called ____________ | preparations |
| Preparation of carboxylic acids: carboxylic acids are typically prepared by __________ reactions | oxidation |
| Preparation of carboxylic acids: What are three oxidation methods that result in a carboxyl group in the products? | oxidation of 1 alcohols, oxidation of alkyl benzenes, and oxidative cleavage of alkynes |
| Preparation of carboxylic acids: primary alcohols are converted to carboxylic acids with _________,_________, or ____ in the presence of ____ and ______ | Na2Cr2O7, K2Cr2O7, or CrO3 in the presence of H2SO4 and H2O |
| Preparation of carboxylic acids: In the oxidation of primary alcohols to form carboxylic acids, both C-H bonds are replaced by _____ bonds | C-O |
| Preparation of carboxylic acids: Alkyl benzenes having at least one benzylic c-H bond are oxidized with ______ to benzoic acid | KMnO4 |
| Preparation of carboxylic acids: in the oxidation of alkyl benzenes, ________ _____ is always the product regardless of the alkyl benzene used as starting material | benzoic acid |
| Preparation of carboxylic acids: in the oxidative cleavage of alkynes both internal and terminal alkynes are cleaved with _______ to give carboxylic acids | ozone ([1] O3 [2] H2O) |
| Preparation of carboxylic acids: In the oxidative cleavage of internal alkynes, what forms as the products? | two carboxylic acids |
| Preparation of carboxylic acids: In the oxidative cleavage of terminal alkynes, what forms as the products? | one carboxylic acidl; the sp-hybridized C-H bond is converted to CO2 |
| Reactions of carboxylic acids: the most important reactive feature of a carboxylic acid is what? | its polar O-H bond, which is readily cleaved with a base |
| Reactions of carboxylic acids: Carboxylic acids react as Bronsted-Lowry acids-- proton ______ | donors |
| Reactions of carboxylic acids: Once a carboxylic acids donates its proton to a strong base, the nonbonded electron pairs on oxygen create electron-rish sites that can be protonated by strong ______ | acids (H-A) |
| Reactions of carboxylic acids: Carboxylic acids are weakly basic and react with strong acids by protonation of the carbonyl oxygen. Why is the carbonyl oxygen protonated rather than OH group? | protonation of the C=O (carbonyl oxygen) is preferred because the resulting conjugate acid is resonance stabilized. |
| Reactions of carboxylic acids: the polar C-O bonds make the carboxy carbon a(n) ______________ | electrophile (Carbon carries a partial + charge) |
| Reactions of carboxylic acids: Because carboxylic acids can be electrophiles, what will they react with? | nucleophiles |
| Reactions of carboxylic acids: explain nucleophilic attack of a carboxylic acid | a nucleophile will attack the electrophilic carbon that results in the cleavage of the pi bond and the addition of the nucleophile |
| carboxylic acids are strong organic Bronsted-Lowry ______ | acids |
| Carboxylic acids are strong B-L acids: because carboxylic acids are strong bronsted-lowry acids, they will readily react with what? | bronsted-lowry bases |
| Carboxylic acids are strong B-L acids: How do you know what bases can be used to deprotonate a carboxylic acid? When does equilibrium favor the products of an acid-base reaction? | when the weaker base and acid are formed in the products |
| Carboxylic acids are strong B-L acids: What is a general rule regarding the ability of a base to deprotonate a carboxylic acid? | an acid can be deprotonated by a base that has a conjugate acid with a higher pKa (a weaker conj acid) |
| Carboxylic acids are strong B-L acids: deprotonation of a carboxylic acid forms what? | a resonance-stabilized conjugate base (carboxylate anion) |
| Carboxylic acids are strong B-L acids: what accounts for why carboxylic acids are more acidic than other compounds with OH bonds (alcohols and phenols) | resonance stabilization (neg. charge on more electronegative atom) |
| Carboxylic acids are strong B-L acids: to understand the relative acidity of ethanol, phenol, and acetic acids, what must we compare? | the stability of their conjugate bases |
| Carboxylic acids are strong B-L acids: to understand the relative acidity of ethanol, phenol, and acetic acids, what must we compare the stability of their conjugate bases and use what rule? | anything that stabilizes a conjugate base A- makes the starting acid H-A more acidic. |
| Carboxylic acids are strong B-L acids: RCOOH, ROH, and C6H5OH are more acidic than most organic hydrocarbons. why? | because of their O-H bond |
| Carboxylic acids are strong B-L acids: summarize the relationship between acidity and stability of the conjugate base | as the stability of the conjugate base increases, the acidity of the starting acid also increases |
| The pKa of a carboxylic acid is affected by nearby groups that _________ donate or withdraw electron density | inductively |
| Inductive effects in aliphatic carboxylic acids: electron-_____________ groups stabilize a conjugate base, making carboxylic acid MORE acidic | withdrawing |
| Inductive effects in aliphatic carboxylic acids: electron-_____________ groups DEstabilize a conjugate base, making carboxylic acid LESS acidic | donating |
| Inductive effects in aliphatic carboxylic acids: The number, electronegativity, and location of substituents also affect acidity. Explain a trend between the # of electronegative substituents and the strength of the acid (acidity) | the larger the number of electronegative substituents, the stronger the acid |
| Inductive effects in aliphatic carboxylic acids: The number, electronegativity, and location of substituents also affect acidity. Explain a trend between the electronegativity of substituents and the strength of the acid (acidity) | the more electronegative the substituent, the stronger the acid |
| Inductive effects in aliphatic carboxylic acids: The number, electronegativity, and location of substituents also affect acidity. Explain a trend between the proximity of an electron-withdrawing group and the strength of the acid (acidity) | the closer the electron-withdrawing group to the COOH, the stronger the acid |
| substituted benzoic acids: substituents on benzene ring either donate or withdraw electron density depending on the balance of their _________ and ___________ effects. These effect determine the acidity of substituted benzoic acids. | inductive and resonance effects |
| substituted benzoic acids: Rule (1) electron-donor groups ____________ a conjugate base, making an acid _____ acidic | destabilize, less |
| substituted benzoic acids: How does an electron-donor group destabilize a conjugate base? (ex: carboxylate anion) | by donating electron density onto a negatively charged carboxylate anion |
| substituted benzoic acids: Rule (2) electron-withdrawing groups ____________ a conjugate base, making an acid _____ acidic | stabilize, more |
| substituted benzoic acids: How does an electron-withdrawing group destabilize a conjugate base? (ex: carboxylate anion) | by removing electron density from the negatively charged carboxylate anion |
| substituted benzoic acids: a benzoic acid substituted by an electron-donating group has a ________ pKa than benzoic acid, while a benzoic acid substituted by an electron-withdrawing group has a _________ pKa than benzoic acid | higher, lower |
| substituted benzoic acids: electron-donating groups ___________ benzene to electrophilic attack while electron-withdrawing groups ___________ benzene to electrophilic attack | activate, deactivate |
| a useful technique called ____________ uses solubility differences and acid-base principles to separate and purify compounds | extraction |
| Extraction: extraction can only separate compounds having different solubility properties by dissolving one layer in an __________ solvent and the other in an __________ solvent | aqueous and organic solvent |
| Extraction: alcohols and carboxylic acids having more than _#_ carbons are water insoluble | 5 |
| Extraction: if two compounds you are trying to separate have similar solubility properties, how could you use extraction to separate them? | if one of the compounds is acidic enough, then acid-base chemistry can be used to change its solubility properties (carboxylic acid) |
| Extraction: a carboxylic acid can be separated from other organic compounds by converting it to a water soluble _________ anion by an acid-base reaction | carboxylate |
| sulfonic acids are very _____ acids because their conjugate bases are resonance stabilized, and all the resonance structures delocalize a negative charge on oxygen | strong acids |
| Sulfonic acids: the sulfonate anions are very stabilized and are therefore _____ bases, making them _____ leaving groups in nucleophilic substitution reactions | weak, good |
| amino acids | contain two functional groups- an amino group (NH2) and a carboxy group (COOH) |
| an amino acid is both an _____ and a _____ | acid and base |
| amino acids are never uncharged neutral compounds. They exist as _____, so they have very high melting points and are very soluble in water | salts |
| the neutral form of an amino acid that carries a positive charge and a negative charge is called a ___________ | zwitterion |
| amino acids can exist in three different forms depending on the ___ of the aqueous solution in which it is dissolved | pH |
| Protonation of amino acids occurs as pH ________ | decreases (becomes more acidic (+)) |
| the pH at which the amino acid exists primarily in its neutral form is called its ____________ ______ | isoelectric point (pI) |
| isoelectric point | average of both pKa values of an amino acid |
Created by:
cmccartney2