CHEM10050 : Gilheany Lecture 9 - Alkynes & Amines

What is an alkyne?

a) A compound that contains one or more C≡C double bonds

b) A compound that contains one or more C≡C triple bonds

c) A compound that contains one or more C-C single bonds

b) A compound that contains one or more C≡C triple bonds

How are alkynes named?

a) They are named using the same method as alkanes

b) They are named using the same method as alkenes

c) They are named using the same method as alkenes, but the name ends in -yne

c) They are named using the same method as alkenes, but the name ends in -yne

What is the simplest alkyne?

a) Ethane

b) Ethene

c) Ethyne

c) Ethyne

What is the hybridization of carbon in a linear alkyne?

a) sp

b) sp2

c) sp3

a) sp

What is the bond angle in a linear alkyne?

a) 90°

b) 120°

c) 180°

c) 180°

What is the use of acetylene in oxyacetylene welding?

a) It is used as a fuel

b) It is used as a reducing agent

c) It is used as an oxidizing agent

a) It is used as a fuel

What is the temperature of the flame in oxyacetylene welding?

a) Nearly 1000 °C

b) Nearly 2000 °C

c) Nearly 5000 °C

c) Nearly 5000 °C

Which of the following is a stable bond in alkynes?

a) C-C single bond

b) C=C double bond

c) C≡C triple bond

c) C≡C triple bond

What is the hybridization of carbon atoms in alkyne compounds with one triple and one single bond?

a) sp hybridization

b) sp2 hybridization

c) sp3 hybridization

a) sp hybridization

How many hybrid orbitals are formed when the s and one p orbital of the carbon atom are hybridized in alkyne compounds?

a) one

b) two

c) three

b) two

What is the shape of sp hybrid orbitals?

a) linear

b) trigonal planar

c) tetrahedral

a) linear

How many p orbitals are unhybridized in sp hybridization?

a) one

b) two

c) three

b) two

What is the energy level of sp hybrids in comparison to sp3 and sp2 hybrids?

a) higher

b) lower

c) same

b) lower

What is the angle between the two sp hybrids in alkyne compounds?

a) 120°

b) 180°

c) 90°

b) 180°

What type of bonds do the remaining two p orbitals form in alkyne compounds?

a) s bonds

b) p bonds

c) dative bonds

b) p bonds

What type of overlap forms the second and third bonds of the C≡C triple bond in alkyne compounds?

a) sigma overlap

b) pi overlap

c) hybrid overlap

b) pi overlap

What type of bonds are formed by the overlap of one of the sp hybrid orbitals on each carbon with s orbitals from H atoms in alkyne compounds?

a) C—C s bond

b) C—H s bonds

c) C—C p bonds

b) C—H s bonds

What is the shape of the remaining two p orbitals in alkyne compounds?

a) linear

b) tetrahedral

c) trigonal planar

a) linear

What is the hybridisation of a carbon atom that has four single bonds?

a) sp hybridisation

b) sp2 hybridisation

c) sp3 hybridisation

c) sp3 hybridisation

What is the hybridisation of a carbon atom that has one double bond and two single bonds?

a) sp hybridisation

b) sp2 hybridisation

c) sp3 hybridisation

b) sp2 hybridisation

How can you determine the hybridisation state of a carbon atom?

a) Count the number of s bonds.

b) Count the number of unhybridised p orbitals.

c) Count the number of lone pairs of electrons.

b) Count the number of unhybridised p orbitals.

What is the shape of a carbon atom that has one triple bond and one single bond?

a) tetrahedral

b) trigonal

c) linear

c) linear

Which type of addition occurs in the hydrogenation of alkynes?

a) anti addition

b) syn addition

c) electrophilic addition

b) syn addition

What is the product of the hydrogenation of an alkyne?

a) alkyne

b) alkene

c) alkane

b) alkene

Why does a reduced activity catalyst have to be used for selective hydrogenation of alkynes?

a) Alkynes are more reactive than alkenes.

b) Alkenes are more reactive than alkynes.

c) Alkanes are more reactive than alkenes.

b) Alkenes are more reactive than alkynes.

Which catalyst is commonly used to selectively hydrogenate alkynes to alkenes?

a) Pd/CaCO3

b) Na/K alloy

c) CuSO4/FeSO4

a) Pd/CaCO3

What type of stereoisomer is formed during syn addition in the hydrogenation of alkynes?

a) cis

b) trans

c) both cis and trans

a) cis

What is the major product of the hydrogenation of an alkyne in the presence of a regular catalyst?

a) alkene

b) alkyne

c) alkane

c) alkane

What is the key factor that makes the carbanion in alkylation reactions of terminal alkynes more stable than an amide ion?

a) The C in the alkyne is sp hybridised

b) The C in the alkyne is sp3 hybridised

c) The C in the alkyne is sp2 hybridised

a) The C in the alkyne is sp hybridised

Which of the following is not true of the lone pair of electrons on C in the carbanion in alkylation reactions?

a) It is in a sp hybrid orbital

b) It is substantially more stable than sp2 or sp3 hybrids

c) It is substantially less stable than an amide ion

c) It is substantially less stable than an amide ion

Which type of alkynes are acidic in alkylation reactions?

a) Only terminal alkynes (C≡C-H)

b) All alkynes

c) Only internal alkynes

a) Only terminal alkynes (C≡C-H)

What is the resulting species when the H of a terminal alkyne is removed by a very strong base, such as NaNH2?

a) A carbanion (carbon-centered anion)

b) A nitrogen anion

c) A hydrogen ion

a) A carbanion (carbon-centered anion)

What type of reaction is the alkylation of terminal alkynes?

a) SN1 substitution reaction

b) SN2 substitution reaction

c) Addition reaction

b) SN2 substitution reaction

What is the purpose of alkylation reactions?

a) To form alkanes from alkenes

b) To form alkenes from alkanes

c) To form more complex products from simple starting materials

c) To form more complex products from simple starting materials

Which type of catalyst is used to selectively make alkenes from hydrogenation of alkynes?

a) Lindlar's catalyst

b) Grignard reagent

c) Birch reduction catalyst

a) Lindlar's catalyst

What is the stereochemistry of the product formed by the syn addition of H atoms to the same side of an alkyne during hydrogenation?

a) Cis

b) Trans

c) There is no stereoselectivity in this reaction

a) Cis

Why is a reduced activity (poisoned) catalyst needed to make alkenes selectively in hydrogenation reactions of alkynes?

a) Alkynes readily undergo hydrogenation to give alkanes

b) Alkynes are more reactive than alkenes

c) Alkynes are less reactive than alkenes

a) Alkynes readily undergo hydrogenation to give alkanes

How can you determine the hybridisation state of a C atom in a carbon compound?

a) Count the number of s bonds

b) Count the number of lone pairs on the C atom

c) Count the number of p bonds

c) Count the number of p bonds

What is an amine?

a) An organic derivative of ammonia containing nitrogen atoms

b) A molecule with triple bonds and nitrogen atoms

c) A molecule with double bonds and nitrogen atoms

a) An organic derivative of ammonia containing nitrogen atoms

How many covalent bonds does a trivalent nitrogen atom have?

a) One

b) Two

c) Three

d) Four

c) Three

What is the shape of an amine molecule when N has three single bonds?

a) Linear

b) Bent

c) Tetrahedral with one corner vacant

d) Square planar

c) Tetrahedral with one corner vacant

What is the bond angle in an amine with pyramidal geometry?

a) 90°

b) 105°

c) 107°

d) 120°

c) 107°

What is the main reason for the reactivity of amines?

a) Strong bonds

b) Weak bonds

c) Presence of lone pair of electrons on N

d) High electronegativity of N

c) Presence of lone pair of electrons on N

Which of the following biomolecules can contain amines?

a) Lipids

b) Proteins

c) Carbohydrates

d) All of the above

b) Proteins

Amines are:

a) Acidic, electrophilic and reducible

b) Basic, nucleophilic and oxidisable

c) Neutral, nonpolar and hydrophobic

d) None of the above

b) Basic, nucleophilic and oxidisable

Which of the following is not a natural product containing amines?

a) Quinine

b) Adrenaline

c) Penicillin

d) Morphine

c) Penicillin

How many lone pairs of electrons does a trivalent nitrogen atom have in an amine?

a) None

b) One

c) Two

d) Three

b) One

What is the shape of an amine molecule when N has four single bonds?

a) Linear

b) Bent

c) Tetrahedral

d) Octahedral

c) Tetrahedral

How many covalent bonds does a trivalent N atom in an amine have?

a) One

b) Two

c) Three

c) Three

Which of the following molecules has a pyramidal geometry?

a) Methane (CH4)

b) Ethylene (C2H4)

c) Ammonia (NH3)

c) Ammonia (NH3)

Why are amines basic?

a) Due to the presence of a lone pair of electrons on N

b) Due to the weak C-N bonds

c) Due to the weak N-H bonds

a) Due to the presence of a lone pair of electrons on N

Which of the following statements about the polarity of amines is true?

a) C-N bonds are significantly polarised

b) N-H bonds are weakly polarised

c) N is significantly less electronegative than H

b) N-H bonds are weakly polarised

Why are small amines relatively soluble in water?

a) Because mixing polar molecules with the very polar water molecules is energetically favourable

b) Because mixing non-polar molecules with the very polar water molecules is energetically favourable

c) Because amines are non-polar

a) Because mixing polar molecules with the very polar water molecules is energetically favourable

Which of the following is not a property of amines?

a) They readily react with acids

b) They readily react with oxidising agents

c) They readily react with reducing agents

c) They readily react with reducing agents

What is the product of the reaction between an amine and an H+ ion?

a) An amide

b) An ammonium salt

c) An alkene

b) An ammonium salt

Which of the following is not true about the basicity of amines?

a) Amines are relatively weak bases compared to hydroxide (HO⁻)

b) Amines are electron-rich

c) Amines react with electron-rich species

c) Amines react with electron-rich species

Which of the following solvents are amines soluble in?

a) Water

b) Non-polar solvents

c) Both a and b

c) Both a and b

What is the geometry of an amine molecule with three single bonds?

a) Linear

b) Trigonal planar

c) Pyramidal

c) Pyramidal.

Why are amines reactive?

a) Due to weak bonds

b) Due to the presence of a lone pair of electrons on nitrogen

c) Due to strong polarity

b) Due to the presence of a lone pair of electrons on nitrogen.

Why are small amines soluble in water?

a) Because they are non-polar

b) Because they form strong covalent bonds with water molecules

c) Because they are polar and form hydrogen bonds with water molecules

c) Because they are polar and form hydrogen bonds with water molecules.

Which of the following is not true regarding the basicity of amines?

a) Amines are electron-rich

b) They readily react with electron-poor species

c) Amines are stronger bases than hydroxide (HO⁻)

c) Amines are stronger bases than hydroxide (HO⁻).

What is the Lewis basicity of amines?

a) Their ability to donate a proton

b) Their ability to accept an electron pair

c) Their ability to donate an electron pair

c) Their ability to donate an electron pair.

What is the reason for the observation that many amine drugs are not very stable to prolonged storage in air?

a) They are highly reactive

b) They contain lone pairs on nitrogen

c) They are highly polar

b) They contain lone pairs on nitrogen

In what form are most amine drugs administered?

a) As free amines

b) As hydrochlorides or related compounds

c) As nitrogen oxides

b) As hydrochlorides or related compounds.

What is an advantage of converting amine drugs into hydrochlorides?

a) Reduced water solubility

b) Increased polarity

c) Reduced crystallinity

b) Increased polarity

Which atoms in amiodarone have the potential to act as bases?

a) Nitrogen atoms only

b) Oxygen atoms only

c) Nitrogen and oxygen atoms

c) Nitrogen and oxygen atoms

Which part of an amine molecule acts as a nucleophile in a reaction?

a) The lone pair of electrons

b) The C-N bond

c) The N-H bond

a) The lone pair of electrons

What is the common product formed when an amine acts as a nucleophile in a reaction?

a) An alkene

b) An alcohol

c) An ammonium salt

c) An ammonium salt