Chp 2 Flashcards
(20 cards)
What are the recommended practice problems from Klein in Chapter 2?
2.1, 2.5, 2.8 (a-f), 2.10, 2.12, 2.14, 2.16, 2.21, 2.23, 2.25, 2.26, 2.32, 2.37, 2.40, 2.43, 2.52, 2.54, 2.58, 2.62 and 2.64
These problems are intended to reinforce concepts related to molecular representations.
What are the characteristics of condensed structures?
No bonds are shown but there is still structural information
Condensed structures provide a simplified view of molecular connectivity.
In bond-line structures, how are carbon atoms represented?
Carbon atoms are not labeled; assumed at every corner or endpoint
This simplifies the representation of organic molecules.
What is the maximum number of bonds that can be drawn to a carbon atom?
4 bonds
Exceeding this would violate the tetravalency of carbon.
What is the bond angle for an sp² hybridized carbon?
120 degrees
This geometry is typical for trigonal planar arrangements.
What are functional groups?
Characteristic groups of atoms/bonds that possess a predictable chemistry
Functional groups determine the chemical reactivity of molecules.
What does IR spectroscopy utilize to cause transitions in vibrational energy levels?
Photons of a certain energy
This technique helps identify functional groups based on their vibrational modes.
What does formal charge impact in molecules?
Stability and reactivity
Understanding formal charge is crucial for predicting molecular behavior.
What is the formula for calculating formal charge?
Formal charge = # normal valence electrons – [electrons in lone pair + ½ of bonding electrons]
This formula helps identify the charge on atoms in a molecule.
What is a carbocation?
A positively charged carbon atom
This occurs when a carbon has three bonds instead of four.
What is a carbanion?
A negatively charged carbon atom
This occurs when a carbon has three bonds and carries a -1 charge.
How are 3D bond-line structures represented on paper?
Using dashed and solid wedges
This indicates groups that point into or out of the paper.
What is resonance in chemistry?
A method representing the distribution of electrons throughout a molecule’s π orbitals
Resonance structures illustrate multiple valid electron arrangements.
What is resonance stabilization?
The spreading of charge that stabilizes a molecule
This occurs when charge delocalization reduces the energy of a molecule.
What do curved arrows indicate in resonance structures?
Electron movement for pairs of electrons
Curved arrows show where electrons are moving from and to.
What are the five main bonding patterns in which resonance occurs?
- Allylic lone pairs
- Allylic positive charge
- Lone pair adjacent to a positive charge
- Pi bond between two atoms with different electronegativities
- Conjugated pi bonds in a ring
Recognizing these patterns helps predict resonance behavior.
What is the significance of filled octets in assessing resonance stability?
The most significant resonance forms have the greatest number of filled octets
Filled octets contribute to the stability of resonance contributors.
What distinguishes localized electrons from delocalized electrons?
Localized electrons are NOT in resonance; delocalized electrons ARE in resonance
Delocalization increases stability in molecules.
What type of hybridization do peptide bonds exhibit?
sp² hybridization
This affects the geometry and rotation around the C-N bond in polypeptides.
How many localized lone pairs are present in a molecule with no unhybridized p orbitals?
0
Localized lone pairs cannot participate in resonance.
