Chapter 13 Homework
Which of the following is not a typical characteristic of an alkyne hydrocarbon? A) water soluble B) lower density than water C) flammable D) boiling point increases with increasing number of carbons.
???? Alkyne hydrocarbons are flammable, they undergo combustion in the presence of oxygen and heat. Consider the typical properties of a compound containing only carbon and hydrogen atoms.
What is the general formula for an alkene? A) CnH2n B) CnH2n+2 C) CnH2n-2 D) C2nHn E) CnHn
A) CnH2n
Which molecular formula corresponds to an alkyne? A) C₈H₁₄ B) C₆H₁₄ C) C₁₀H₂₂ D) C₃H₆ E) C₂H₆
A) C₈H₁₄ Due to the presence of a triple bond, alkynes have four fewer hydrogens than the corresponding saturated, alkane CnH2n+2CnH2n+2 and will adopt the general formula CnH2n−2CnH2n−2, where n is any number equal to two or greater. C₈H₁₄ shares this general formula indicating it can be an alkyne.
In a hydrogenation reaction of an alkene, hydrogen atoms are added to a double bond to form an __________. A) alkane B) alkene C) alkyne D) aromatic ring Question
A) alkane An alkane is formed. When hydrogen (H₂) adds to a double bond, each carbon atom gains one hydrogen atom and the double bond become a single bond.
What is the major product of the reaction shown below?
A) butane The reaction of alkene with hydrogen in the presence of a metal catalyst such as platinum or palladium leads to the formation of an alkane. Thus hydrogenation of 2-butene leads to the formation of butane as the product.
In a ___________ reaction, the components of water (H-OH) are added across a carbon-carbon double bond (C=C). A) hydration B) hydrogenation C) bromination D) combustion E) elimination
A) hydration Hydration reaction. A hydration reaction involves adding the components of water (H-OH) across a carbon-carbon double or triple bond.
What type of reaction converts 4-decene into decane? A) hydrogenation B) hydration C) halogenation D) hydrohalogenation E) halohydrogenation
A) hydrogenation The conversion involves addition of hydrogen atoms to the double bonded carbons, so the process is called hydrogenation.
Alkyne hydrocarbons have similar properties to their analogous alkenes and alkanes. Which of the following is not a typical characteristic of an alkyne hydrocarbon? A) water soluble B) lower density than water C) flammable D) boiling point increases with increasing number of carbons.
A) water soluble Alkyne hydrocarbons are not water soluble because they are relatively non-polar compounds, containing only carbon and hydrogen atoms.
Determine the correct name for the cycloalkene shown here.
B) 1,3-dimethylcyclohexene The compound contains six carbons in a ring, with a double bond in the ring and two methyl groups attached. The ring positions are numbered with the double bond positioned between carbons 1 and 2, with the direction of the numbering giving the lowest numbering for the two methyl substituents. Numbering the double bond position would therefore be redundant. So the name would be 1,3-dimethylcyclohexene.
Correctly name the alkyne shown here.
B) 1-bromo-1-butyne The chain has four carbons and a triple bond so it is a butyne. Number from the end that gives the lowest number for the triple bond, so the name is 1-bromo-1-butyne.
What is the major product of the reaction shown below? C=C-C --> HCl A) 1-chloropropane B) 2-chloropropane C) 3-chloropropane D) 1-chloro-1-propene E) No reaction occurs.
B) 2-chloropropane The hydrohalogenation reactions converts an alkene into a haloalkane. The halogen substituent favors addition at the more substituted, secondary carbon over addition at less substituted, primary carbons.
Determine the number of carbon atoms in 3-hexene? A) 5 B) 6 C) 7 D) 8 E) 9
B) 6 The alkene is 3-hexene has the prefix hex- which corresponds to six carbon atoms.
What reagents are required to convert ethene to 1-bromoethane? A) H₂ B) HBr C) H₂O, H₂SO₄ D) Br₂
B) HBr HBr will add to the double bond of ethene, with H adding to C1 and Br adding to C2 to form 1-bromoethane.
What reagents are required to convert 1-butene to butane? A) Br₂ B) H₂ C) H₂O, H₂SO₄ D) HBr
B) H₂ H₂ will add to the double bond of 1-butene, with H adding to C1 and H adding to C2 to form butane.
Alkenes contain what type of carbon-carbon bond? A) single bond B) double bond C) triple bond D) aromatic
B) double bond
The simplest alkyne is acetylene, C₂H₂. What is the IUPAC name of acetylene? A) 2-butyne B) ethyne C) ethylene D) ethaneyne E) acetylyne
B) ethyne The simplest alkane with two carbons is ethane. Change the "a" to "y" to name an alkyne, so the name is ethyne.
Which compound corresponds to an unsaturated hydrocarbon? A) 1-butanol B) trans-3-heptene C) cis-2,3-dibromohexane D) 3-chloropentane E) butanoic acid
B) trans-3-heptene Hydrocarbons are compounds that only contain carbon and hydrogen and are classified on the types of carbon-carbon bonds. Unsaturated hydrocarbons have carbon atoms that share at least one double or triple bond. trans-3-heptene is an alkene containing a carbon-carbon double bond and is an unsaturated hydrocarbon.
How many hydrogen atoms are in 4-methyl-2-pentyne? A) 8 B) 9 C) 10 D) 11 E) 12
C) 10 Skeletal structures are written where only the bonds between carbon and non-hydrogen atoms are shown. The carbon atoms and the hydrogen atoms attached to them are not shown. The number of hydrogens on the carbon atom is 4 - n, where n is the number of bonds to that carbon.In 4-methyl-2-pentyne, there are 10 hydrogen atoms with a molecular formula of C₆H₁₀.
What reagents are required to convert 1-propene to 1,2-dibromopropane? A) HBr B) H₂O, H₂SO₄ C) Br₂ D) H₂
C) Br₂ Br₂ will add to the double bond of 1-propene, with Br adding to C1 and Br adding to C2 to form 1,2-dibromopropane.
Which molecular formula corresponds to an alkene? A) C₈H₁₄ B) C₆H₁₄ C) C₂H₄ D) C₁₁H₂₄ E) C₄H₆
C) C₂H₄ Due to the presence of a double bond, alkenes have two fewer hydrogens than the corresponding saturated, alkane CnH2n+2CnH2n+2 and will adopt the general formula CnH2nCnH2n, where n is any number equal to two or greater. C₂H₄ shares this general formula indicating it can be an alkene.
Cyclopentene is treated with hydrogen gas (H₂) and a platinum catalyst to form the product cyclopentane. This reaction can be generally classified as what type of process? A) oxidation B) elimination C) addition D) substitution
C) addition This is an addition reaction. An addition reaction involves adding two components across a double bond. In a hydrogenation reaction, the components of H-H are added across the double bond to convert an alkene to an alkane.
The reaction of an alkene with water produces what type of product? A) alkane B) alkyne C) alcohol D) aldehyde E) amino acid
C) alcohol When water adds to a double bond, one of the carbons gains a hydrogen and one gains an -OH group. Organic compounds with -OH functional groups are called alcohols.
All of the following statements about alkene hydrocarbons are true except: A) alkenes contain carbon-carbon double bonds (C=C). B) alkenes that contain only carbon and hydrogen atoms have low water solubility. C) alkene hydrocarbons are polar compounds. D) alkenes undergo addition reactions. E) alkenes can form chains or cyclic structures.
C) alkene hydrocarbons are polar compounds. Alkenes containing only carbon and hydrogen atoms are non-polar compounds.
The molecules 1-butene and trans-2-butene are A) identical molecules. B) stereoisomers. C) constitutional isomers. D) isotopes. E) molecular isomers.
C) constitutional isomers.
Alkynes contain what type of carbon-carbon bond? A) single bond B) double bond C) triple bond D) aromatic
C) triple bond
Which of the following is a valid IUPAC name for an alkyne? A) 1,3-dimethyl-3-hexyne B) trans-2-pentyne C) 2-methyl-2-butyne D) 2-chloro-3-hexyne E) cis-3-octyne
D) 2-chloro-3-hexyne A triple bond is linear so there is no cis-trans isomerism. A methyl group on carbon 1 of an alkyne would extend the chain by one carbon, placing the triple bond in position 2. There is no room for a substituent on either carbon that is part of a triple bond. So the only name that describes a possible compound is 2-chloro-3-hexyne.
How many carbon atoms are present in cycloheptene? A) 4 B) 5 C) 6 D) 7 E) 8
D) 7 Cycloheptene has seven carbon atoms as indicated by the prefix hept-.
What type of product is formed in the hydration of 1-butyne? A) alcohol B) enol C) aldehyde D) ketone E) carboxylic acid
D) ketone The addition of BH₃ and then H₂O₂, OH⁻ proceeds in a concerted mechanism where the hydrogen acts as a nucleophile adding to the more substituted carbon and the hydroxy adding to the less substituted carbon following anti-Markovnikov's regioselectivity
What is the major product of the reaction of 2-hexyne with excess bromine? A) 2-bromohexene B) 2,3-dibromohexene C) 2-bromohexane D) 2,3-dibromohexane E) 2,2,3,3-tetrabromohexane
E) 2,2,3,3-tetrabromohexane After one molecule of bromine adds to 2-hexyne forming 2,3-dibromo-2-hexene, with excess bromine a second molecule adds to the double bond forming 2,2,3,3-tetrabromohexane. Not D) 2,3-dibromohexane The complete halogenation of an alkyne produces a tetrasubstituted alkyne.
