Ch. 1 - Structure and Bonding Flashcards
What is deuterium?
isotope of hydrogen (one proton, one neutron) (mass # = 2)
also relates to NMR spectroscopy!
Where are most elements in organic chemistry found within the periodic table?
1st and 2nd rows (s and p orbitals)
Which is higher in energy, s or p orbitals? Why?
p orbitals are higher in energy because the electron density is farther away (takes work to pull electron away, takes work to shield?)
What is electronegativity?
tendency to gain electrons
What is the formula for formal charge?
FC = val e- – (1/2 bonding + nonbonding e-)
What is an isomer?
same molecular formula, different structure + molecule
What atoms are common exceptions to octet rule? (BBPS)
boron and beryllium (2nd row; not enough e- in neutral molecule)
phosphorus, silver (3rd row; empty d orbitals, can have more than 8)
Where is hydrogen placed for all oxyacids? (ex. HNO3)
it is placed on oxygen
Where does organic chem assume hydrogens go?
on carbon
What does “resonance stabilized” mean?
molecule has 2 or more resonance structures; negative charge is spread over molecule aka electrons are delocalized
What is the formal charge of a single bonded oxygen with 3 lone pairs?
-1
What is the formal charge of a double bonded oxygen with two lone pairs?
0
What is curved arrow notation?
shows how electron position differs between structures
What is a heteroatom?
an atom other than carbon or hydrogen
What are the only things that vary for resonance strucutres?
lone pairs and pi bonds (and formal charge)
What is the most electronegative element?
fluorine
What is the 2nd most electronegative element?
oxygen
What are the 3rd most electronegative elements?
nitrogen and chlorine
What is a resonance hybrid?
composite of all possible resonance structures, electrons are delocalized
Why can carbon form four bonds where it should only have two open p orbitals?
It hybridizes to 4 sp3 hybrid orbitals
Which is stronger, a sigma bond or a pi bond?
a sigma bond is stronger because the electron density is closer to the nuclei (in between)
What type of overlap occurs in sigma and pi bonds?
sigma = end-end pi = side-side
What is conjugation?
- double/triple bonds that are separated by a single bond
- occurs whenever p orbitals can overlap 3 adjacent atoms
- conjugated systems have added stability
What makes a better resonance structure?
- more bonds and fewer formal charges
- obeys octet rule
- negative charge is on more electronegative atoms
- positive charge is on less electronegative atoms
- PRIORITIZE OCTET
What is the difference between a shell and an orbital?
Shell = principal quantum number/orbit Orbital = actual electron density
How many orbitals are in the first shell?
one
Where is most of the volume of an atom contained?
electron cloud
Does a chemical bond produce a system of higher or lower energy?
lower
Atoms bond in order to achieve a full shell of _____ electrons, leading to a system that has _____ energy and increased stability, compared to the unbonded atoms.
valence; decreased
T or F: A p orbital has the greatest electron density at the nucleus.
F, A p orbital has a node (region of zero electron density) at the nucleus.
What is a constitutional isomer?
An isomer that has different connectivities (same molecular formula)
T or F: Halogens are usually placed in the periphery of the molecule because they only form one bond.
False. That’s hydrogen.
T of F: B and Be do not have sufficient electrons to have an octet.
True
T or F: A resonance hybrid is a single structure.
True. It does not fluctuate between the resonance forms.
What two things determine an atom’s geometry?
bond angle and bond length
What is the basic principle of VSEPR theory?
groups around an atom are located as far from each other as possible
T or F: The number of unpaired (single) electrons in a resonance structure cannot change.
True
T or F: Lone pairs are omitted in condensed structures.
True (double check!)
What two things does a charge on an atom indicate in a skeletal structure?
the number of covalent bonds and nonbonded electrons pairs at that atom
What type of symmetry does a sigma bond have?
cylindrical symmetrical
What is the ground state of an atom?
the lowest energy state of an atom where all electrons are in their lowest energy level
When drawing a condensed structure of an organic compound, multiple bond lines are usually ______ while single bond lines are often ______.
Included, omitted
For a carbon-carbon triple bond, what oritals overlap to form a sigma bond?
sp
Unhybridized p orbitals are at what angle towards hybrid orbitals?
right angle
T or F: Electronegativity is a relative quantity?
true
What is the electronegative scale values?
0 to 4
What is percent s character in sp, sp2 and sp3?
50%, 33%, 25%
T or F: Any carbon-hydrogen bond is always considered to be polar.
False
T or F: Pi bonds in a triple bond are perpendicular planes to each other.
true
REMEMBER: Whenever C or H are bonded to O or N and halogens, they are polar!
Remember this!
