ochem ch9 – Chemistry – Flashcards

Unlock all answers in this set

Unlock answers
question
How many distinct alkynes exist with a molecular formula of C4H6?
answer
2
question
Give the IUPAC name for HC-=CCH2CH2CH3.
answer
pent-1- yne
question
Draw an acceptable structure for acetylene.
answer
H-C-=C-H
question
Give the IUPAC name for Cl3CCH2CH2CH2C≡CH.
answer
6,6,6-trichlorohex- 1-yne
question
Provide the IUPAC name for Cl3C(CH2)3C≡CH.
answer
6,6,6-trichloro- 1-hexyne or 6,6,6-trichlorohex- 1-yne
question
Provide the IUPAC name for (CH3)2CHCH2CH(OH)CH2C≡CCH3.
answer
2-methyl- 6-octyn- 4-ol or 2-methyloct- 6-yn- 4-ol
question
Draw an acceptable structure for hepta-3,6- dien-1-yne
answer
HC-=CCH=CHCH2CH=CH2
question
Give the IUPAC name for CH3CH=CHCH=CHC-=CCH3.
answer
octa-2,4- dien-6- yne
question
Which of the following improperly describes the physical properties of an alkyne?
answer
insoluble in most organic solvents
question
Which of the following alkynes has the lowest boiling point?
answer
3,3-dimethyl- 1-butyne
question
The pi bond of an alkyne is ________ and ________ than the pi bond of an alkene.
answer
shorter, weaker
question
How many moles of oxygen are required in the complete combustion of 1 mole of acetylene?
answer
2.5
question
What products result when calcium carbide is combined with water?
answer
acetylene and calcium hydroxide
question
How many moles of water are produced when one mole of propyne undergoes complete combustion?
answer
2
question
The carbon-carbon triple bond of an alkyne is composed of ________.
answer
one σ bond and two π bonds
question
In trans-hept- 4-en- 2-yne the shortest carbon-carbon bond is between carbons ________.
answer
2 and 3
question
Which of the species below is less basic than acetylide?
answer
CH3ONa
question
Among the compounds water, but-1- yne, but-2- yne, and ethane, which are stronger acids than ammonia?
answer
water and but-1- yne
question
To a solution of propyne in diethyl ether, one molar equivalent of CH3Li was added and the resulting mixture was stirred for 0.5 hour. After this time, an excess of D2O was added. Describe the major organic product(s) of this reaction.
answer
CH3C-=CD + CH4
question
What is the pKa of a terminal alkyne?
answer
25
question
Why are terminal alkynes more acidic then other hydrocarbons?
answer
The carbanion which results upon deprotonation of a terminal alkyne has the lone pair of electrons in an sp hybrid orbital. The greater % s character of this orbital gives this orbital a significantly lower energy.
question
Which of the following bases will favorably deprotonate a terminal alkyne? (More than one answer is possible.)
answer
A) n-BuLi B) LDA D) PhMgBr (Ph=phenyl)
question
Describe a qualitative, nonspectroscopic means for distinguishing terminal alkynes from internal ones.
answer
Add a solution of Cu+ or Ag+. Terminal alkynes react to form insoluble metal acetylides which precipitate
question
Which of the following bases are sufficiently strong to deprotonate a terminal alkyne with an equilibrium constant greater than 1?
answer
2) lithium diisopropyl amide 3) n-butyl lithium 4) phenylmagnesium bromide
question
Describe a sequence of reactions by which hept-3- yne can be straightforwardly prepared from acetylene.
answer
1. NaNH2 2. CH3CH2Br 3. NaNH2 4. CH3CH2CH2Br
question
Describe a sequence of reactions by which butylbenzene can be straightforwardly prepared from phenylacetylene.
answer
1. NaNH2 2. CH3CH2Br 3. H2, Pt
question
2-Methylhex- 3-yne can be prepared by the reaction of an alkynide with an alkyl halide. Does the better synthesis involve alkynide attack on bromoethane or on 2-bromopropane? Explain your reasoning.
answer
Attack on the primary bromide (bromoethane) is much more favorable. Reaction of an alkynide with the secondary bromide would result mostly in elimination instead of substitution.
question
Describe a sequence of reactions by which 1-propylcyclohexan- 1-ol can be straightforwardly prepared from propyne.
answer
1. NaNH2 2. cyclohexanone 3. H+, H2O 4. H2, Pt
question
Why is a terminal alkyne favored when sodium amide (NaNH2) is used in an elimination reaction with 2,3-dichlorohexane?
answer
The strong base deprotonates the terminal alkyne and removes it from the equilibrium.
question
When 2,2-dibromobutane is heated at 200°C in the presence of molten KOH, what is the major organic product?
answer
but-2- yne
question
Describe a sequence of reactions by which hept-1- yne can be straightforwardly prepared from hept-1-ene.
answer
1. Br2 2. NaNH2, heat
question
Treatment of hex-2- yne with mercuric sulfate in dilute sulfuric acid yields a mixture of two ketones. Similar treatment of hex-3- yne produces a single ketone instead of a mixture. Explain.
answer
The two carbons of the triple bond in hex-3- yne are equivalent, and only 3-hexanone results. In the case of hex-2- yne, the two carbons of the triple bond are not equivalent, and a mixture of 2- and 3-hexanone results.
question
Which of the following describes an unsymmetrical addition reaction?
answer
propyne with 1 mole HBr
question
Name the compound which results when pent-2- yne is subjected to catalytic hydrogenation using a platinum catalyst.
answer
pentane
question
Describe a sequence of reactions by which trans-pent- 2-ene can be straightforwardly prepared from propyne.
answer
1. NaNH2 2. CH3CH2Br 3. Na, NH3
question
Which of the following reagents should be used to convert hex-3- yne to (E)-hex- 3-ene?
answer
Na, NH3
question
Which of the following reagents should be used to convert hex-3- yne to (Z)-hex- 3-ene?
answer
H2, Lindlar's catalyst
question
A mixture of hept-1- yne, hept-2- yne, and hept-3- yne was hydrogenated in the presence of a platinum catalyst until hydrogen uptake ceased. If one assumes that the hydrogenation went to completion, how many different seven-carbon hydrocarbons were produced?
answer
1
question
________ is produced when 1 equivalent of HBr is added to hex-1- yne in the presence of peroxides.
answer
A mixture of E and Z isomers of 1-bromohex- 1-ene
Get an explanation on any task
Get unstuck with the help of our AI assistant in seconds
New