chemistry ch 14.15.16.18 – Flashcards

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The one aldehyde and the one ketone with a molecular formula of C3H6O are stereoisomers
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false
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Aldehydes and ketones both contain a carboxyl group
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false
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The VSEPR model predicts bond angles of 180° about the carbonyl carbon of aldehydes and ketones
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false
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The carbonyl carbon of a ketone is not a stereocenter.
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true
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The one aldehyde and the one ketone with a molecular formula of C3H6O are constitutional isomers
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true
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Aldehydes and ketones both contain a carboxyl group.
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false
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The VSEPR model predicts bond angles of 120° about the carbonyl carbon of aldehydes and ketones.
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true
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The carbonyl carbon of a ketone is a stereocenter
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false
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Aldehydes, Ketones and Carboxylic acids
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contain carbonyl groups, They are highly polar molecules.They boil at higher temperatures.Lower members are soluble in water because they can form H-bond with water. Higher members are insoluble in water due to large size of their hydrophobic group.
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ethers
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hydrocarbons and weakly polar compounds
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Aldehydes are prepared by
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a.Dehydrogenation of primary alcohols b. Controlled oxidation of primary alcohols. c. Controlled and selective reduction of acyl halides Aromatic aldehydes can be prepared bya. Oxidation of toluene with chromyl chloride or CrO3 in the presence of acetic anhydride b. Formylation of arenes with carbon monoxide and Hydrochloric acid in the presence of anhydrous aluminiumchloride / Cuprous chloride c. Hydrolysis of benzal chloride
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Ketones are prepared by
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bya. oxidation of secondary alcohols b. Hydration of alkenes c. Reaction acyl chlorides with dialkylcadmium d. By friedel crafts reaction Carboxylic acids are prepared by - a. oxidation of primary alcohols, aldehydes and alkenes b. hydrolysis of nitriles c. Treatment of grignard reagent with carbondioxide.
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CARBOXYLIC ACID
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Carboxylic acids having an ? - hydrogen are halogenated at the ? -position on treatment with chlorine or bromine in the presence of small amount of red phosphorus to give ? -halocarboxylic acids.
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ESTERIFICATION
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Carboxylic acids react with alcohols or phenols in the presence of a mineral acid such as conc.H2SO4 as catalyst to form esters.
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Aldehyde
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Many fragrances are aldehydes. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group, which is any generic alkyl or side chain.
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Aldehydes
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The group without R is called the aldehyde group or formyl group. Aldehydes differ from ketones in that the carbonyl is placed at the end of a carbon skeleton rather than between two carbon atoms.
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Many aldehydes have pleasant odours
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The double bond between carbon and oxygen is characteristic of all aldehydes and is known as the carbonyl group.
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aldehyde condensed structural formulas
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?CHO. Using this convention, the formula of formaldehyde is HCHO and that of acetaldehyde is CH3CHO
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The functional group of an alcohol is the -OH (hydroxyl) group
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true
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The parent name of an alcohol is the name of the longest carbon chain that contains the -OH group.
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true
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In the IUPAC system, the presence of three -OH groups is shown by the ending -triol.
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true
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Because of the presence of an -OH group, all alcohols are polar compounds.
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true
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The boiling point of alcohols increase with increasing molecular weight.
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true
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What is the difference in structure between a primary, a secondary, and a tertiary alcohol?
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The difference is in the number of carbon atoms bonded directly to the carbon bearing the -OH group. For primary alcohol, there is zero or one carbon group; for a secondary alcohol, there are two, and for a tertiary alcohol, there are three.
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Explain in terms of noncovalent interactions why the low molecular weight alcohols are soluble in water but the low molecular weight alkanes and alkynes are not
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Low molecular weight alcohols form hydrogen bonds with water molecules through both the oxygen and hydrogen atoms of their - OH groups, and because of this association, they dissolve in water. Low molecular weight alkanes, alkenes, and alkynes are nonpolar compounds and do not associate in any way with water molecules. The large amount of hydrogen bonding between an alcohol molecule and water molecules makes the low molecular weight alcohol soluble in water. Low molecular weight alkanes, alkenes, and alkynes are insoluble in water.
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Why does the water solubility of low molecular weight alcohols decrease as molecular weight increases
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As the molecular weight of an alcohol increase, the hydrocarbon part of the molecule becomes a larger and larger part of its surface area. In other words, as the hydrocarbon portion increases, the nonpolar region of the compound increases as well. The physical properties of alcohols, including their solubility in water, then become more like those of hydrocarbons of similar carbon skeletons.
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-propanol (isopropyl alcohol) is commonly used as rubbing alcohol to cool the skin. 2-hexanol, also a liquid, is not suitable for this purpose. Why?
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The cooling effect comes from evaporation. 2-hexanol's boiling point is too high to be easily evaporated from the skin.
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. The two most important reactions of alcohols are their acid-catalyzed dehydration to give alkenes and their oxidation to aldehydes, ketones, and carboxylic acids.
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true
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The acidity of alcohols is comparable to that of water.
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true
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Acetic acid, CH3COOH, can be prepared from ethylene, CH2=CH2 by treatment with K2Cr2O7/H2SO4
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true
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Show how to distinguish between cyclohexanol and cyclohexene by a simple chemical test. Tell what you would do, what you would expect to see, and how you would interpret your observations.
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Cyclohexene will react with bromine (a reddish-purple liquid) to give 1,2-dibromocyclohexane, which has no color. Cyclohexanol does not react with bromine. Therefore, the liquid that causes the reddish-purple of bromine to disappear must be cyclohexene.
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The functional group of thiol is the -SH (sulfhydryl) group
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true
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The parent name of thiol is the name of the longest carbon chain that contains the -SH group.
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true
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thiol
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Organic compounds containing sulfhydryl groups.
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The S - H bond is nonpolar covalent.
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true
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The acidity of ethanethiol is comparable to that of phenol.
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true
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Both phenols and thiols are classified as weak acids
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true
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Explain why glycerol is much thicker (more viscous) than ethylene glycol, which in turn is much thicker than ethanol.
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The thickness (viscosity) of these three liquids is related to the degree of hydrogen bonding between their molecules in the liquid state. Hydrogen bonding is strongest between molecules of glycerol, weaker between molecules of ethylene glycol, and weakest between molecules of ethanol.
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The acidity of ethanethiol is comparable to that of phenol.
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true
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Both phenols and thiols are classified as weak acids.
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true
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The most common biological reaction of thiols is their oxidation to disulfides
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true
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The functional group of a disulfide is the - S - S - group.
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true
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Explain why methanethiol, CH3SH, has a lower boiling point (6oC) than methanol, CH3OH (65oC), even though methanethiol has a higher molecular weight
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Molecules of methanol, in the liquid state, associate by hydrogen bonding. Molecules of methanethiol, in the liquid state, associate only by the considerably weaker London dispersion forces. Because of the stronger intermolecular forces of attraction between its molecules, methanol has a higher boiling point than methanethiol.
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Today, the major carbon sources for the synthesis of methanol are coal and methane (natural gas), both nonrenewable resources.
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true
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. Intermolecular acid-catalyzed dehydration of ethanol gives diethyl ether.
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true
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. Conversion of ethylene to ethylene glycol involves oxidation to ethylene oxide, followed by acid-catalyzed hydration (addition of water) to ethylene oxide
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true
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Ethylene glycol is soluble in water in all proportions.
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true
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A major use of ethylene glycol is as automobile antifreeze.
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true
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. The one aldehyde and the one ketone with a molecular formula of C3H6O are constitutional isomers. True .b. Aldehydes and ketones both contain a carbonyl group True c. The VSEPR model predicts bond angles of 120o about the carbonyl carbon of aldehydes and ketones. True d. The carbonyl carbon of a ketone is a stereocenter. False
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. What is the difference in structure between an aromatic aldehyde and an aliphatic aldehyde? The carbonyl carbon of an aldehyde is bonded to, at least, one hydrogen. The carbonyl carbon of a ketone is bonded to two carbon groups.
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a. An aldehyde is named as an alkanal, and a ketone is named as an alkanone. True b. The names for aldehydes and ketones are derived from the name of the longest carbon chain that contains the carbonyl carbon. True c. In an aromatic aldehyde, the carbonyl carbon is bonded to an aromatic ring. True
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a. The reduction of an aldehyde always gives a primary alcohol. True b. The reduction of a ketone always gives a secondary alcohol. True c. The oxidation of an aldehyde gives a carboxylic acid. True d. The oxidation of a primary alcohol gives a ketone. False e. Tollen's reagent can be used to distinguish between an aldehyde and a ketone. True f. Sodium borohydride, NaBH4, reduces an aldehyde to a primary alcohol. True g. The addition of one molecule of alcohol to the carbonyl group of a ketone gives a hemiacetal. True h. The reaction of an aldehyde with two molecules of alcohol gives an acetal, plus a molecule of water. True i. The formation of hemiacetals and acetals is reversible. True j. The cyclic hemiacetal formed form 4-hydroxypentanal has two stereocenters and can exist as a mixture of 22 = 4 stereoisomers. True
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Acetone is completely soluble in water, but 4-heptanone is completely insoluble in water. Explain.
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The carbonyl group of acetone forms hydrogen bonds with water. These hydrogen bonds are sufficient to make acetone in any proportions soluble in water. 4-heptanone contains a carbonyl group, which through its hydrogen bonding with water molecules, promotes water solubility. It also contains two 3-carbon hydrocarbon groups bonded to the carbonyl carbon, which inhibit hydrocarbon groups bonded
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Pentane, 1-butanol, and butanal all have approximately the same molecular weights but different boiling points. Arrange them in order of increasing boiling point. Explain the basis for your ranking.
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Pentane is a nonpolar hydrocarbon, and the only attractive forces between its molecules in the liquid state are the very weak London dispersion forces. Pentane, therefore, has the lowest boiling point. Butanal and 1-butanol are both polar molecules. Because 1-butanol has a polar -OH group, its molecules can associate by hydrogen bonding. The intermolecular attraction between molecules of 1-butanol is greater than those between molecules of butanal. 1-butanol, therefore, has a higher boiling point than butanal.
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a. The reduction of an aldehyde always gives a primary alcohol. True b. The reduction of a ketone always gives a secondary alcohol. True c. The oxidation of an aldehyde gives a carboxylic acid. True d. The oxidation of a primary alcohol gives a ketone. False e. Tollen's reagent can be used to distinguish between an aldehyde and a ketone. True f. Sodium borohydride, NaBH4, reduces an aldehyde to a primary alcohol. True
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The addition of one molecule of alcohol to the carbonyl group of a ketone gives a hemiacetal. True h. The reaction of an aldehyde with two molecules of alcohol gives an acetal, plus a molecule of water. True i. The formation of hemiacetals and acetals is reversible. True j. The cyclic hemiacetal formed form 4-hydroxypentanal has two stereocenters and can exist as a mixture of 22 = 4 stereoisomers. True
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What is the characteristic structural feature of a hemiacetal? Of an acetal?
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The characteristic structural feature of a hemiacetal is a carbon atom bonded to an -OH group and either an -OR or an -OAr group. The characteristic structural feature of an acetal is a carbon atom bonded to two -OR or -OAr groups.
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hemiacetal
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When an aldehyde reacts with an alcohol, a_________is formed.
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What is the difference in meaning between the terms "hydration" and "hydrolysis"? Give an example of each.
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Hydration refers to the addition of one or more molecules of water to a substance. An example of hydration is the acid-catalyzed addition of water to propene to give 2-propanol.
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Hydrolysis refers to the reaction of a substance with water
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generally with the breaking (lysis) of one or more bonds in the substance. An example of hydrolysis is the acid-catalyzed reaction of an acetal with a molecule of water to give an aldehyde or ketone and two molecules of alcohol. Another example of hydrolysis is the reverse of Fischer esterification (Chapter 18), namely the hydrolysis of an ester to give a carboxylic acid and an alcohol.
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The general name of an aliphatic carboxylic acid is alkanoic acid. True b. The molecule containing two COOH groups is called a dicarboxylic acid. True c. Ethanedioic acid (oxalic acid) is the simplest decarboxylic acid. True d. 3-methylbutanoic acid is chiral. False
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. The simplest carboxylic acid is methanoic acid (formic acid), HCOOH. True f. Benzoic acid is an aromatic carboxylic acid. True g. Formic acid, which is the common name for HCOOH, is derived from the word formica, which is the Latin name for ants. True h. (S)-lactic acid, CH3-CHOH-COOH contains two functional groups: a 2o alcohol and a carboxyl group. True
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Define and give an example of Fischer Esterification.
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Fischer esterification is the process of forming an ester by treating a carboxylic acid with an alcohol in the presence of an acid catalyst, commonly sulfuric acid. An example is the formation of ethyl ethanoate from ethanoic acid and ethanol
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With three areas of electron density around a carbonyl carbon, the VSEPR theory predicts a bond angle of 120o.
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A trigonal planar atom cannot be a stereocenter. An atom that is a stereocenter must have four different substituents bonded to it.
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Carboxylic acids do not oxidize any further with chromic acid. The conversion of a carboxylic acid to an alcohol is actually a reduction reaction that is accomplished with lithium aluminum hydride (LiAlH4) followed by the addition of an aqueous acid.
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The functional groups of a carboxylic acid are a carbonyl group bonded to a hydroxyl group. True
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structural and physical properties of alcohol.
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The electronegativity of oxygen contributes to the unsymmetrical distribution of charge, creating a partial positive charge on the hydrogen and a partial negative charge on the oxygen. This uneven distribution of electron density in the O-H bond creates a dipole. Also, because of the high electronegativity of oxygen relative to that of carbon, the O-H bond is shorter
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apply IUPAC nomenclature and common names to alcohols.
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Substitutive names of alcohols are developed by identifying the longest continuous chain that bears the hydroxyl group and replacing the -e ending of the corresponding alkane by the suffix -ol.
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Alcohols occur with primary, secondary and tertiary structures. Whether an alcohol is primary, secondary or tertiary depends on the number of hydrogens attached to the carbon atom bearing the -OH group, as shown in the below figure. These differences in structure affect the way the alcohols react.
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?Primary alcohols have two hydrogens on the OH-bearing carbon - this carbon is bonded to one other carbon. ?Secondary alcohols have two carbons and only one hydrogen substituted onto the OH-bearing carbon. ?Tertiary alcohols have three carbons and no hydrogens on the OH-bearing carbon
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As well as having varying numbers of alkyl or aryl groups within the molecules, alcohols may have varying numbers of -OH groups.
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Molecules with two -OH groups are known as diols and those with three -OH groups as triols.
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hydrogenation reaction
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it require heat in the present of catalyst, HYDROGEN IS ADDED H2
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HALOGENATION REACTION symmetrical
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HALOGEN IS ADDED (F.CL.I) EACH CARBON DOUBLE BOND NOT CATALYST IS NEEDED.
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unsymmetrucal HYDROHALOGENATION addition reaction
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hydrogen halide is added (x=f.cl.br.I)
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Hydration reaction is adding water, the product is alcohol
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water is added hydrogen atom to one carbon and OH group to other carbon H2SO4 is required as a catalyst.
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THIOLS -analog of alcohol, strong odor, LOWER BP due to lack of hydrogen bonds.
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contains sulfhydryl groups- SH instead of -OH thiols same as alcohol except that the -OL(methanol) became THIOL(methyl mercaptan, CH3-SH)METHANETHIOL.
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Properties of Thiol are easily oxidized forming disulfides.
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Each thiol loses on H atom and S atom to form disulfide group. and contribute to protein structure.
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thiols
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r- sH + sH -r----->[O]---> r- S- S- r + 2H
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THIOLETHER is a organic compound in which SULFER.
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sulfur atom is bonded to two atoms by single bonds the sulfur.
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carbonyl group all have trigonal planar structure, there are five classes compound.
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a carbon atom double bonded with a Oxigen atom C == O is polar but C=C is nonpolar
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ALDEHYDES; carbonyl
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carbonyl is attached to at Least on H atom.
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KETONE
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carbonyls directly attached to two other carbon atoms
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CARBOXYLIC ACIDS
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Carbonyl carbon atom is bonded to a hydroxyl group -OH
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esters
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esters have fruity smells
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NOMENCLATURE of CARBOXYLIC ACIDS/Bp's higher than alcohols of similar molecular weight Strong, often repellant odors - Crushed ants - Vinegar - Rancid butter - Goat body parts
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Add the -oic acid suffix (and any multiplier prefix) STEP 3. Identify branches
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cyclo COOH
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Benzoic acid
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NOMENCLATURE of ESTERS
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Replace -ic acid with the -ate suffix
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PHYSICAL PROPERTIES of ESTERS Solubility like that of ketones • Floral, fruity odors
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Weakly polar (not as polar as ketones) • Bp's like those of hydrocarbons of similar molecular weight
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The general name of an aliphatic carboxylic acid is alkanoic acid.
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true
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The molecule containing two COOH groups is called a dicarboxylic acid.
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true
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The simplest carboxylic acid is methanoic acid (formic acid), HCOOH
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true
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Formic acid, which is the common name for HCOOH, is derived from the word formica, which is the Latin name for ants.
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true
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(S)-lactic acid, CH3-CHOH-COOH contains two functional groups: a 2o alcohol and a carboxyl group
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true
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Draw a structural formula for methyl 2-hydroxybenzoate.
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COOCH3 OH
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