Molecular Orbital Theory and Hybridization in Organic Chemistry

What are the two basic types of orbitals that can result from orbital combinations?

Hybrid orbitals and molecular orbitals.

What is hybridization theory?

A theory that explains the actual shapes of molecules by invoking the formation of hybrid orbitals during or prior to the bonding process.

What is the geometry of methane (CH4)?

Tetrahedral, with bond angles of 109.5 degrees.

What must happen to the paired electrons in carbon's 2s orbital for bonding to occur?

They must become unpaired.

What is the process called that leads to the formation of sp3 hybrid orbitals?

sp3 hybridization.

What is the general formula for alkanes?

CnH2n+2, where n is the number of carbon atoms.

What type of bonding occurs when atomic orbitals overlap head to head?

Sigma bonding.

What are hydrocarbons?

Substances containing only carbon and hydrogen.

How are alkanes characterized in terms of hybridization?

All carbon atoms are sp3-hybridized and all bonds are single bonds.

What is the shape of sp3 hybridized orbitals?

They form a tetrahedral shape.

What happens to the energy of orbitals during hybridization?

Their energies are equalized to form new equivalent orbitals.

What are the three major categories of hydrocarbons?

Alkanes, alkenes, and alkynes.

What is the simplest alkane?

Methane (CH4).

What is the bond angle in a tetrahedral molecule?

109.5 degrees.

What is the significance of VSEPR theory in molecular geometry?

It predicts the arrangement of orbitals to minimize electron pair repulsion.

What are branched alkanes?

Alkanes that have carbon chains with branches, differing from linear structures.

What is the role of unpaired electrons in bonding?

Only unpaired electrons can form bonds with other atoms.

What is the difference between hybrid orbitals and molecular orbitals?

Hybrid orbitals result from combinations within a single atom, while molecular orbitals result from combinations between atoms.

What is the molecular formula for ethane?

C2H6.

What is the molecular formula for propane?

C3H8.

What is the molecular formula for butane?

C4H10.

What is the significance of the energy gap between the 2s and 2p orbitals in carbon?

It allows for the promotion of an electron to facilitate bonding.

How do sp3 hybrid orbitals orient themselves in 3-D space?

They orient themselves to be as far apart from each other as possible.

What is isobutane?

A branched alkane with the formula C4H10.

What does the term 'sigma bond' refer to?

A type of covalent bond formed by head-to-head overlap of atomic orbitals.

What is the structure of a linear alkane?

A straight chain of carbon atoms connected by single bonds.

What type of overlap do hybrid orbitals undergo when forming covalent bonds?

Mostly head to head overlap.

What are sigma bonds?

Covalent bonds formed by head to head overlap of orbitals.

Give an example of sigma bonding.

The bond between two hydrogen atoms.

What type of bonds are present in alkanes?

Only sigma bonds, also known as single bonds.

What is the zig-zag structure in alkanes due to?

The 109.5° angle between C-C bonds.

What notation is used to simplify the representation of alkanes?

Line-angle formulas.

What does each point or end of a zig-zag line in line-angle formulas represent?

Carbon atoms.

What is the hybridization process that creates sp2 orbitals?

Combining one s orbital and two p orbitals.

What is the geometry of sp2 hybridized orbitals?

Trigonal planar configuration with 120° angles.

What type of bond is formed by sp2 orbitals?

A sigma bond.

What type of bond is formed by unhybridized p orbitals?

A pi bond.

How do sigma and pi bonds differ in terms of strength?

Sigma bonds are stronger and shorter; pi bonds are weaker and longer.

What is the simplest alkene called?

Ethene.

What is the relationship between pi electrons and their reactivity?

Pi electrons are more readily available and easier to break compared to sigma electrons.

What happens to pi electrons during chemical reactions?

They can become delocalized and move between atoms.

What is the ideal angle between sp2 orbitals?

120°.

What is the significance of the zig-zag structure in alkanes?

It reflects the tetrahedral arrangement of sp3 hybridized carbon atoms.

What is the role of the unhybridized p orbital in sp2 hybridization?

It remains unaffected and is positioned at right angles to the sp2 orbitals.

What type of hydrocarbons contain at least one pi bond?

Alkenes.

What is the line-angle representation for propane equivalent to?

CH3CH2CH3.

What does the term 'localized' refer to in the context of sigma electrons?

Sigma electrons are tightly bound to the nucleus and do not move much.

What is the effect of sideways overlap in pi bonds?

It results in weaker bonds compared to head to head overlap in sigma bonds.

What is the implication of the bond strength difference between sigma and pi bonds?

It affects the chemical reactivity of molecules containing these bonds.

What is the structure of ethane in terms of sp3 hybridization?

It consists of two sp3 hybridized carbon atoms forming C-C sigma bonds.

What does the term 'de-localized' mean in relation to pi electrons?

Pi electrons can spread over several atoms in a molecule.

What are the two types of bonds formed when sp2 hybridized carbon atoms bond?

A sigma bond from sp2 orbitals and a pi bond from unhybridized p orbitals.

What is the general formula for open chain monoalkenes?

CnH2n, where n is the total number of carbon atoms.

What type of bond do alkenes contain?

At least one double bond.

What is the geometry around the carbons in an alkyne?

Linear geometry with an ideal angle of 180°.

What is the general formula for open chain monoalkynes?

CnH2n-2, where n is the total number of carbon atoms.

What hybridization does carbon undergo in alkynes?

sp hybridization.

How many orbitals are formed during sp3 hybridization of nitrogen?

Four equivalent sp3 orbitals.

What is the ideal bond angle for sp3 hybridized nitrogen?

109.5°.

What type of hybridization occurs in oxygen when it forms water?

sp3 hybridization.

What is the geometry of sp2 hybridized oxygen?

Trigonal planar geometry with an ideal angle of 120°.

What type of bond is formed between sp2 hybridized carbon and oxygen?

A double bond (C=O) consisting of a sigma bond and a pi bond.

What is the hybridization of nitrogen when forming a C=N double bond?

sp2 hybridization.

What happens to the geometry of sp3 hybridized nitrogen when bonded to hydrogen?

It distorts the tetrahedral angle due to lone pair repulsion.

What is the significance of lone pairs in Lewis structures?

They are often omitted unless specifically needed for clarity.

What is the hybridization and geometry of carbon in a C=C double bond?

sp2 hybridization with trigonal planar geometry.

What is the main characteristic of sp hybridization?

It involves the formation of two sp orbitals and results in triple bonds.

What is the angle between sp hybrid orbitals?

180°.

How does the hybridization of atoms affect bond formation?

Atoms must have the same hybridization to form double or triple bonds.

What type of bonds do sp3 hybridized atoms typically form?

Single bonds.

What is the hybridization of carbon in ethene?

sp2 hybridization.

What is the effect of electronegativity on the C=O bond?

The oxygen atom attracts bonding electrons more strongly than carbon, making the bond polar.

What is the hybridization of carbon in acetylene?

sp hybridization.

What is the bond angle in sp2 hybridized carbon?

120°.

What is the role of unhybridized p orbitals in double bonds?

They overlap sideways to form a pi bond.

What is the hybridization of carbon in 1-butyne?

sp hybridization.

What type of bond does sp2 hybridization allow for?

Double bonds.

What is the geometry of sp3 hybridized oxygen in water?

Distorted tetrahedral due to lone pairs.