Alkenes and Alkynes Quiz

A hydrocarbon with one or more carbon-carbon double or triple bonds, or benzene-like rings.

A hydrocarbon containing a carbon-carbon double bond, with the formula CnH2n.

A hydrocarbon containing a carbon-carbon triple bond, with the formula CnH2n-2.

Different isomers with restricted rotation around a C-C double bond; groups are either on the same or opposite sides of the double bond.

Isomer where identical groups are on the same side of the double bond.

Isomer where identical groups are on opposite sides of the double bond.

A double bond consists of one sigma (σ) bond and one pi (π) bond. The sigma bond is formed by an overlap of sp2 hybrid orbitals, and the pi bond is formed by an overlap of parallel 2p orbitals.

A triple bond consists of one sigma (σ) bond and two pi (π) bonds, formed by overlap of sp hybrid orbitals and two sets of parallel 2p orbitals.

Use the infix "-en-" for carbon-carbon double bonds. Number the parent chain to give the first double bond carbon the lowest number. Follow IUPAC rules for numbering and naming substituents.

Some small alkenes are mainly known by their common names rather than IUPAC names.

Use the infix "-yne-" for carbon-carbon triple bonds. Number the carbon chain to give the first triple bond carbon the lowest number. Following IUPAC rules applies.

Configuration determined by the orientation of atoms along the main chain.

Assign priority to substituents. Z: higher priority groups on same side. E: higher priority groups on opposite sides.

Priority is based on atomic number. If not clear, move to the next atom. Double/triple bond atoms considered equivalent single bonds to multiple same atoms.

Assign a priority to substituents (atoms) on the double bond carbons.

IUPAC naming system governs naming and numbering for alkenes and alkynes following specific rules.

Terminal alkynes are more acidic than alkanes and alkenes due to the stability of their conjugate base anions.

The % s character of the orbital bearing the negative charge in the anion determines the stability of the anion, which in turn affects the acidity of the parent compound.

In a terminal alkyne, the carbon atom involved in the triple bond is sp hybridized, meaning it has 50% s character, which leads to a more stable anion and thus a stronger acid compared to sp² and sp³ hybridized carbons.

Anions with more s character in the orbital holding the negative charge are more stable. This is because s orbitals are closer to the nucleus and more electronegative.

A terminal alkyne is an alkyne with a triple bond at the end of the carbon chain, giving it a hydrogen atom bonded to the sp hybridized carbon.

Cycloalkenes with fewer than 8 carbons have 'cis' configuration; cyclooctenes accommodate 'trans' configuration.

For an alkene with n double bonds and cis-trans isomerism, 2^n isomers are possible.

Vitamin A is an 'all-trans' isomer with 5 double bonds, but its 4 isomeric double bonds can exhibit cis-trans configuration.

They are nonpolar and similar to alkanes with analogous carbon skeletons; they are insoluble in water, and dissolve in each other and non-polar solvents; they are less dense than water in liquid form.

Water (pKa 15.7) is stronger acid than terminal alkynes; therefore, hydroxide ion is not strong enough base for the reaction.

Alkane and alkene hydrogen is not acidic enough to be removed by any base.

The IUPAC name for alkenes uses the infix '-en-' to indicate the presence of a carbon-carbon double bond.

When naming alkenes, the carbon chain is numbered so that the first carbon of the double bond receives the lowest possible number.

The IUPAC name for alkynes uses the infix '-yne-' to indicate the presence of a carbon-carbon triple bond.

When naming alkynes, the carbon chain is numbered so that the first carbon of the triple bond receives the lowest possible number.

The E,Z system assigns a priority to the substituents on each carbon of the double bond based on atomic number, higher atomic number gets higher priority.

In the E,Z configuration, a configuration is assigned Z (zusammen, together) if the groups of higher priority are on the same side of the double bond.

In the E,Z configuration, a configuration is assigned E (entgegen, opposite) if the groups of higher priority are on opposite sides of the double bond.

A terminal alkyne, having a hydrogen attached to a sp hybridized carbon, is more acidic than alkanes and alkenes due to the high s character of the sp orbital, leading to a more stable conjugate base anion.

Terminal alkynes are acidic because the sp hybridized carbon, holding the acidic hydrogen, has a 50% s character. This high s character contributes to the stability of the conjugate base anion, making the parent alkyne more acidic.

Water (pKa 15.7) is a stronger acid than terminal alkynes. Therefore, the hydroxide ion is not a strong enough base to deprotonate a terminal alkyne.

Unsaturated hydrocarbons contain one or more carbon-carbon double or triple bonds, or benzene-like rings.

Cis-trans isomerism refers to different arrangements of groups around a carbon-carbon double bond.

A trans alkene is more stable than a cis alkene due to less nonbonded interaction strain between alkyl substituents.

A double bond consists of one sigma bond (sp2 hybridized) and one pi bond (formed by overlapping p orbitals).

A triple bond consists of one sigma bond (sp hybridized) and two pi bonds (formed by overlapping p orbitals).

A phenyl group is derived from benzene, and it's relatively unreactive under many conditions.

To assign E or Z configuration, compare atomic numbers of groups attached to the double bond carbons. Higher atomic number = higher priority.

Cycloalkenes with rings smaller than 8 carbons can only have a cis configuration, where substituents on the double bond are on the same side.

The sp hybridized carbon in a terminal alkyne creates a more stable conjugate base anion through increased s character, leading to greater acidity.

While terminal alkynes are acidic, they aren't acidic enough for hydroxide ions to deprotonate them, as water is a stronger acid.

Alkanes and alkenes are generally not acidic - their hydrogen atoms are very difficult to remove.