Organic Chemistry- Bonding Flashcards
What does bonding determine?
How atoms come together to form molecules. It also govers the ways those molecules interact with the other molecules in their environment.
Organic chemistry is the study of what?
Carbon and carbon-containing compounds.
What makes carbon so important?
Carbon has unique bonding properties. Carbon is tetravalent, which means that is can form bonds with up to four other atoms, allowing for the massive versatility required to form the foundation of biomolecules and life itself.
Why can carbon form bonds with many different elements?
Because of its moderate electronegativity
Because carbon atoms are small, the bonds are what?
The bonds are strong and stable
What are the two types of chemical bonds?
Ionic
Covalent
What are ionic bonds?
Electrons are transferred from one atom to another and the resulting ions are held together by elecctrostatic interactions
What are covalent bonds?
Electrons are shared between atoms
Organic chemistry usually uses which type of chemical bond?
Covalent bonding
The 1st three quantum number n, l, ml, describe what?
The size, shape, number, and orientation of atomic orbitals an element possess.
The principle quantum number, n, corresponds to what?
The energy level of a given electron in an atom and is essentially a measure of size
The smaller the principle quantum number, the ________.
The closer the shell is to the nucleus and the lower the energy
The MCAT will most likley on test principle quantum numbers 1 to What?
7
What is the range for the azimuthal quantum number?
0 to n-1.
The l-values 0,1,2,3 correspond to what?
The s, p, d, f subshells
What increases as the azimuthal quantium number increases?
Energy increases
What is within each subsehll?
Several orbitals
Orbitals are described by the what?
Magnetic quantum number
What is the range of the magnetic quantum number?
-1 to +1
An s-orbital is what shape?
Spherical and symetrical, centered around the nucleus
A p-orbital is what shape?
Composed of two lobes located symmetrically about the nucleus and contains a node, an area where the probability of finding an electron is zero- at the nucleus. Picture the p-orbital as a dumbell that can be psotioned in three different orientations. Along the x y and z axsis
A d-orbital is composed of what? What shape?
Four symmetrical lobes and contains two nodes. Four of the d-orbitals are clover shaped, and the fifth looks like a donut wrapped around the center of a p-orbital
Each orbital can hold how many electrons, with what spin quantum numbers?
Two electrons
+1/2 and -1/2
When two atomic orbitals combine, they form what?
Molecular orbitals
How are molecular orbitals obtained?
Mathmatically by adding or subtracting the wave functions of the atomic orbitals.
Will the mathmatics of containing wave functions be tested on the MCAT?
No, but some questions may ask for the visualization of molecular orbitals
If the signs of the wave functions are the same, what will be produced?
Lower-energy (more stable) bonding orbital is produced
If the signs of the wave functions are different, what will be produced?
Higher-energy (Less stable) antibonding orbitals
When a molecular orbital is formed by head-to-head or tail-to tail overlap, the resulting bond is called what?
a sigma bond
All single bonds are what type of bonds?
sigma bonds accommodating two electrons
When two p-orbitals line up in a parallel fashion, their electron clouds overlap and form what type of bond?
Pi bond
What is a double bond?
A pi bond on top of an existing pi bond is a double bond
What is a triple bond?
A sigma bond and two pi bonds
Single bonds allow what? Double and triple bonds hinder what?
Free rotation,
Double and triple hinder rotation, and lock the atom in position
Can a pi bond exist indepndently of a sigma bond?
No, ONly after the formation of a sigma bond will the p-bond be able to develop
The more bonds that ar formed between atoms, the shorter ____________.
The overall bond length
List the bond lengths from longest to shortest.
Single
Double
Triple
Shorter bond lengths are ________ and require more ________.
stronger than longer bonds and require more energy to break
________ bonds are weaker then _______ bonds. Therefore it is possible to what?
Individual pi bonds are weaker than sigma bonds, Therefore, it is possible to break only one of the bonds in a double bond, leaving a single bond intact
What makes for stiffer molecules? Explain?
Double bonds in compounds. Partial double-bonds character in structures with resonance also restricts free rotation.
Proteins exhibit this kind of limited rotation because there is resonance in the amide linkages between adjacent amino acids.
Carbon has an electron configuration of what?
1s^2 2s^2 2p^2
How many electrons does carbon need to finish its octet?
four electrons
What is inconsistent about the molecule methane and our knowledge of the asymmetrical districution of carbon’s valence electrons?
The 4 sigma bonds in methane are equivalent.
The inconsistency seen in Methane can be accounted for by what theory?
Hybridization
How are hybrid orbitals formed?
By mixing diferent types of orbitals. Just as with molecular orbitals, we can use advanced mathmatics to merge three p-orbitals and one s-orbital.
What is the result of hybrid molecules?
Four identical sp^3 orbitals with new, hybridized shapes.
What is the forming geometry of the sp^3 hybridized orbital?
All four of these orbitals point toward the vertices of a tetrahedral geometry.
How does the hybridization take place?
By promoting one of the 2s electrongs into the 2pz-orbital. This produces four valence orbitals, each iwth one electron.
How do you determine how much “s characcter” a certain hybrid orbital has?
Determine what type of bygridization exists and use the name to solve the problem.
For example, in sp^3 orbitals, we have one s- and three p-orbitals, so the bond has 25% s character and 75% p character.
Carbon is most often bonded with what type of hybridization?
sp^3
What are the two other hybridizations?
sp^2
sp
sp^2 hybridization is seen in what?
alkenes
In sp^2 hybridization, what is left unhybridized? What does it participate in?
The third p-orbital of each carbon is unhybridized. This participates in a pi bond.
The 3 sp^2 orbitals are oriented _____ degrees apart?
120degrees which allows for maximum separation
Can sp^2 orbitals bond?
Two sp^2 hybridized orbitals will participate in C-H bonds, and the other hybrid orbital will line up with the pi bond and form the sigma component of the C=C double bond.
What are sp hybridized bonds for?
To form a triple bond. Two fo teh p-orbitals will form pi bonds and the third p-oribital will combine with the s-orbital to form two sp-bonds.
sp bonds have _____% s and _____% p character.
50%
50%
sp orbitals are oriented _____ degrees apart.
180 degrees
Where can the two pi bonds be in an sp hybridized carbon?
between the carbon and one other atom (forming a triple bond, like ethyne) or between the carbon and two different atoms (forming two double bonds ina row, like carbon dioxide).
Resonance delocalization occurs in what molecules?
Molecules that have conjugated bonds
Conjugation requires what? Why?
Alternating single and multiple bonds because this pattern aligns a number of unhybridized p-oribitals down the backbone of the molecule
What do pi electrons do when molecules have conjugated bonds?
Delocalize through this p-orbital system, adding stability to the molecule
How are resonance structures drawn?
As the various transient forms the molecule takes
Do resonance structures show the true form a hybrid might take? Why?
No,
These forms aren’t in any sort of equilibirum–the elctron density is distributed throughout, making the true form a hybrid of the resonance structures.
If the stability of the various resonance forms differ, then the true electron density will favor what?
The most stable form
Why can particular resonance structures be favored?
They lack formal charges or form full octets on highly electronegative atoms like oxygen and nitrogen
What can also favor certain resonance structures?
Stabilization of positive and negative charges through induction and aromaticity
