Orgo exam #1

What type of bond has equal sharing of e-

Covalent

Two atoms share, but one puts e- more than the other

Polar covalent

One atom fully gives an e- to another (oppositely charged on each side)

Ionic

How many e- domains does a linear molecule have

2

How many e- domains does a trigonal planar molecule have

3

How many e- domains does a tetrahedral molecule have

4

Which bonds result in an end on overlap

Sigma

Which bonds result in side on overlap

Pi

What bonds do p orbitals have to be (end/side on)

Side on

How many pi and sigma bonds are in a triple bond

One sigma and two pi

Atomic orbital vs molecular orbital

Atomic = region of space around an atom

Molecular = region of space around a whole molecule

When do bonds form

When atomic orbitals overlap and mix

Lumo

Lowest unoccupied molecular orbital

Homo

Highest occupied molecular orbital

Number of atomic orbitals in = # of what

Molecular orbitals out

How do you calculate sp hybridization

1 - # of domains

You never move _____ bonds in resonance structures, only _____ and ____ bonds

Sigma, LPs, Pi

What are the allowed resonance structure moves

LP to pi, pi to pi, and pi to lp

What is special about resonance arrows

They are double headed

3 guiding principles for resonance structures

(in most significant) atoms have full octets, least amount of charges, negative charge on the more electronegative atom

If in phase > out of phase

(out of phase =) bonding

If in phase = out of phase

(out of phase =) non-bonding

If in phase < out of phase

(out of phase =) antibonding

Saturated alkane

made of C + H with no pi bonds (only c-h or c-c) and no compound has more than twice the amount of H as there is C

Can alkanes have pi bonds

No

Molecule naming convention

prefix-locant-parent-suffix

1 carbon = what alkane name

Methane

2 carbons = what alkane name

Ethane

3 carbons = what alkane name

propane

4 carbons = what alkane name

Butane

_______ don’t count when alphabetizing

Prefixes

What does the ending of group 7A atoms change to when naming

-O

More branching = ______ boiling point and why

Lower because the surface area is decreased, meaning the dispersion forces are fewer and weaker

When drawing resonance structures what do you have to draw explicitly

All hydrogens and LPs

More branching = _____ stable and ____ deltaH combustion

More, smaller

Conformations in order of decreasing energy

Eclipsed, staggered, chair

Constitutional isomer

Compounds with the same molecular formula but are bonded in a different arrangement

Boiling and melting points _______ with molecular weight

Increase

Torsional strain

Results from repulsion of e- held close together in eclipsing bonds

Gauche confirmation

Staggered confirmation where alkyl groups are adjacent - not the lowest, not the highest

What should you consider when picking a resonance structure

octet, fewest FCs, (-) on more EN atom, simplest, overall FC does not change

FC calculation

(# ideal ve-) - (# lone e-) - (# bonds)

Isomer

Molecules that have the same chemical formula but are arranged differently

Anti-confirmation

Newman projection - two alkyl groups are 180 degrees apart, lowest energy

Steric strain

Repulsion between bulky groups that are too close in space

Why are cycloalkanes bigger than propane not flat

Because C atoms prefer a bond angle of 109.5, flat rings would force them into unnatural bond angles (angle strain) the C-H bonds would also line up (eclipsing)

Why are chair conformations the most stable

Angle strain

Deviation from ideal sp3 angles (109.5)

What cycloalkane has the lowest energy and why

Cyclohexane because it has the most flexibility and can get the closest to ideal bond angles

Why are chair confirmations the most stable conformation of an alkane

Because they are completely staggered

Cycloalkane confirmations (lowest energy to highest energy)

Chair, twist-boat, boat, half chair

1,3-diaxial interactions

Type of steric strain that happens when two groups sticking straight up or straight down get too close (major culprit of steric strain, gauche interaction)

What does wavenumber represent

Frequency

What does a strong sharp peak at ~1700cm-1 indicate

C = O (Carbonyl)

What does a strong peak at ~1700 and a broad peak slightly above 3000 indicate

Carboxyllic acid

What does a broad peak centered around 3000cm-1 indicate

O-H (Alcohol)

What does 1 or 2 medium sharp peak(s) above 3000cm-1 indicate

N-H(1 or 2) - Amine

What does it mean if you see an odd mass in a mass spec problem

There is an odd number of N

What is the equation for degrees of uncertainty

DU = (2 * C) + 2 - #H - #X + #N / 2

If you see an IR peak higher than 2900 what does that indicate

Single bond

If you see an IR peak between 1500 and 2000 what does that indicate

Double bond

If you see an IR peak between 2000 and 2900 what does that indicate

Triple bond

Order of sp hybridiztion strength

sp > sp² > sp³

How do you know if an IR is showing an alkene vs an alkyne

Alkene = peak at ~1650, Alkyne = peak ~3300

How do you know if there is a terminal alkyne or an internal alkyne on an IR

Terminal: C-H spike and C☰C spike
Internal: wont have these features

What should you do when you see 4 DU

Think of an arene

Base peak

Tallest peak of a mass spec - most stable fragment

What are the two isotopes for bromine

79 and 81

What are the two isotopes for chlorine

35 and 37

1680

Amide

1710

Aldehyde

1725

Ester