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CHM231 Ch.8
| Question | Answer |
|---|---|
| What's the functional group of an alcohol? | The -OH group bonded to an sp3 hybridized carbon |
| What's it called if an -OH group is bonded to an sp2 hybridized carbon? | phenol or enol |
| What's the difference between a primary, secondary, & tertiary alcohol? | The -OH is on a primary, secondary, or tertiary carbon |
| If a compound contains two -OH groups, what is it called? | A diol |
| If a compound contains three -OH groups, what's it called? | A triol |
| What's an unsaturated alcohol? | An alcohol that contains an -OH and a C=C double bond |
| Are alcohols polar or nonpolar? | Polar |
| What two bonds in an alcohol are polar covalent? | C-O & O-H |
| What are the only intermolecular forces that occur in nonpolar molecules? | London [Dispersion] Forces |
| What types of molecules do London [Dispersion] forces occur in? | Alkanes, alkenes, & alkynes |
| Are London Forces weak or strong, and how do their strengths change? | Weak, and the force increases with the number of electrons in the molecule |
| Do Dipole-dipole interactions occur on polar or nonpolar molecules? | Polar |
| What type of molecules do dipole-dipole interactions occur on? | Haloalkanes |
| What's a hydrogen bond? | An attractive force between a positively-charged H on one atom and a negatively-charged O or N on another atom |
| What molecules do hydrogen bonds occur on? | Alcoholes, amines, amino acids, & carboxylic acids |
| Which have higher boiling points: Alcohols or hydrocarbons, and why? | Alcohols, hydrogen bonds |
| Which has higher solubility: Alcohols or hydrocarbons, and why? | Alcohols, hydrogen bonds |
| What are hydrophilic molecules? Give examples | Molecules that are soluble in water; Polar molecules (like alcohols & acids), hydrogen bonds |
| What's another name for hydrophobic? | Lipophilic |
| What are hydrophobic molecules? Give examples. | Those that are insoluble in water and are soluble in nonpolar solvents; Apolar molecules (like alkanes, alkenes, & alkynes), London forces |
| What are amphiphilic molecules? Give an example. | Molecules with polar and apolar parts, so they can have long hydrophobic chains with polar groups at the end of the chain; Fatty acids |
| How does chain length affect boiling point and why? | As chain length increases, boiling point increases because of increasing London forces |
| What are two examples of where hydrogen bonds occur in the biology world? | DNA & cellulose |
| How do alcohol's acidity compare to water's? | Alcohol's is about the same acidity or slightly weaker than water |
| As the acid strength increases, the pKa will increase or decrease? | Decrease |
| When a strong acid is present, what does the oxygen atom of an alcohol behave like? | A weak base |
| What does the proton transfer from a strong acid to a weak base create? | An oxonium ion |
| What are two examples of molecules that are amphoteric? | Water & alcohols |
| What does amphoteric mean? | A molecule has characteristics of both an acid & a base and can act as either |
| What do you need to do to convert an alchol to an alkyl halide? | Substitute the -OH for a halogen |
| Is OH- a good or poor leaving group and why? | Poor leaving group because it's a strong base |
| What are the most common reagents that can convert an OH- into a better leaving group? | Halogen acids, HX, thionyl chloride, & SOCl2 |
| What mechanism do tertiary alcohols use to react with an HX? | Sn1 |
| What are the steps for the reaction of a tertiary alcohol with HX? | A proton attaches to the oxygen of the alcohol, an H2O is lost from the oxonium ion giving a tertiary carbocation intermediate, and then a reaction with the halide ion occurs |
| What mechanism do primary alcohols use to react with an HX? | Sn2 |
| What are the steps for the reaction of a primary alcohol with HX? | A proton attaches to the OH- giving H2O, and a nucleophilic substitution occurs and H2O is replaced by the halogen ion |
| What type of reaction in haloalkanes is the reaction of a tertiary alcohol with HX similar to? | Sn1 |
| What type of reaction in haloalkanes is the reaction of a parimary alcohol with HX similar to? | Sn2 |
| Between Sn1 & Sn2 reactions, which are governed by steric factors & which are governed by electronic factors? | Sn1 = electronic, Sn2 = steric factors |
| What is the most widely-used reagent for converting alcohols to alkyl chlorides? | thionyl chloride (SOCl2) |
| What's splenda and what is it molecularly? | An artificial sweetener, sucralose |
| Of the three, do primary, secondary, or tertiary alcohols require the highest temperature to be converted to an alkene through beta-elimination? | Primary alcohols |
| Do higher reaction temperatures favor nucleophilic substitutions or beta-eliminations in alcohols? | Beta eliminations |
| What's the equation for the change in Gibbs free energy? | ΔG = ΔH – TΔS; (ΔG = Gibbs free energy, ΔH = enthalpy, T = temperature [K], ΔS = Entropy [measure of disorder]) |
| What two reactions can occur in the dehydration of alcohols? | Nucleophilic substitutions & beta eliminations |
| What does Zaitsev's rule say about alcohol dehydration? | When more than one alkene can be obtained, the more stable alkene will be the major product |
| How does dehydration of a secondary alcohol occur? | Proton transfer from an H3O creates an oxonium ion and a water molecule; H2O is lost & leaves a carbocation intermediate + water; Proton transfer gives an alkene & regenerates the acid catalyst |
| How does dehydration of a primary alcohol occur? | proton transfer of Alcohol + H3O → oxonium ion + H2O; Proton transfer gives H3O + alkene + H2O |
| Explain hydration-dehydration equilibrium. | Adding water to an alkene gives an alcohol, and taking away water from an alchol gives an alkene |
| Do large amounts of water favor alkene or alcohol formation? | Alcohol |
| Does the scarcity of water favor alkene or alcohol formation? | Alkene |
| What type of molecules can primary alcohols be oxidized to? | Aldehydes or carboxylic acids |
| What type of molecules can secondary alcohols be oxidized to? | Ketones |
| What type of molecules can tertiary alcohols be oxidized to? | Actually, oxidation doesn't occur without breaking C-C bonds |
| What is the most common oxidizing agent of alcohols? | Chromic acid, H2CrO4 |
| What molecule do you use to oxidize a primary alcohol to an aldehyde? | PCC |
| What does PCC stand for? | Pyridinium chlorochromate |
| Does PCC oxidize C=C double bonds? | No |
| Are ethers polar or nonpolar, and why? | Polar because the C-O bonds are polar-covalent |
| What type of interactions occur in pure ethers? | Dipole-dipole interactions |
| In solutions with water, what type of molecules are ethers? | Hydrogen-bond donors |
| Compare the boiling points of alkanes, alcohols, and ethers | Alcohol > ether > alkanes |
| Describe the bonds and solubilities of alcohols, ethers, and alkanes | Bonds: alcohol = hydrogen bonds, ether = dipole-dipole interactions, alkanes = London forces; solubility: alcohol = in water, ether = mostly in water, alkane = insoluble in water |
| What's Williamson ether synthesis? | When an ether is formed from an organohalide & an alcohol |
| Why are ethers excellent solvents in which to carry out organic reactions? | They have good solvent properties and are generally inert to chemical reactions |
| What prefix & suffix do cyclic ethers contain? | Ox- & -ane |
| How many atoms are in a ring with the suffix -irane? | 3 |
| How many atoms are in a ring with the suffix -etane? | 4 |
| How many atoms are in a ring with the suffix -olane? | 5 |
| How many atoms are in a ring with the suffix -ane? | 6 |
| How are cyclic ethers prepared? | Nucleophilic substitution |
| What's an epoxide? | A cyclic ether in which oxygen is one atom of a three-membered ring |
| How reactive are epoxides to aqueous acid? | Readily & very reactive, due to the angle strain in the three-membered ring |
| What does the reaction of an epoxide with an aqueous acid give? | A glycol |
| What's a thiol? | A molecule containing an -SH group bonded to an sp3 hybridized carbon |
| What suffix is used with thiols? | -thiol |
| What prefix is used with the common names of thiols? | Mercapto- |
| Low-molecular-weight thiols have a __. Give examples | Stench (like those present in the scent of skunks & in natural gas odorants) |
| How are thiols' polarity, and why? | Low in polarity because C & S have the same electronegativity |
| How are thiols boiling points and solubility compared to alcohols? | Lower & less soluble than alcohols |
| How are thiols acidity compared to alcohols? | Stronger acids than alcohols |
| What do thiols + strong bases form? | Salts |
| What are thiols oxidized to? | Disulfides |
| What can disulfides easily be reduced to? | Thiols |
| What does a disulfide refer to? | Usually a linked pair of Sulfur atoms |
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