O Chem 1

Question 1

Hydrocarbons

Answer 1

Organic compound containing C and H atoms only.

Meth- 1C 
Eth- 2C
Prop- 3C
But- 4C
Pent- 5C
Hex- 6C
Hept- 7C 
-ane, -ene, -yne -> depend on type of bonds present.

Question 2

Alkane

Answer 2

only single bonds between C atom (saturated hydrocarbons) : CnH(2n+2).

Question 3

Alkene

Answer 3

contain at least one C=C (carbon to carbon double bond): CnH(2n).

Question 4

Alkyne

Answer 4

Contain at least one carbon to carbon triple bond: CnH(2n-2).

Question 5

Aromatic

Answer 5

cyclic molecule with resonance (contains benzene-like molecule).

Question 6

Ring strain

Answer 6

of cyclic hydrocarbons:
-Sp^3 carbon atoms are tetrahedral therefore prefer to have a bond angle of 109.5.

-In a ring structure, the bond angle between attached carbons is often significantly below 109.5 -> destabilizing.

Question 7

Degrees of Unsaturation (DoU)

Answer 7

Indicates number of pi bonds and/or rings.
-1 ring: 1 DoU; 1 pi bond= 1 DoU

• Double bond: 1 DoU
• Triple bond: 2 DoU
• Benzene: 4 DoU
• DoU = (2C+2-H)/2
• C: # carbons, # hydrogens and/or halogens
• If nitrogen present, count as one additional C and one additional H.

Question 8

Carbocation

Answer 8

Molecule with a carbon atom that has a +1 charge (only has 3 bonds to it).

-Doesn’t have full octet; unstable

Question 9

Carbanion

Answer 9

Molecule with a carbon atom that has a -1 charge (has 3 bonds to it plus a lone pair).

-Has full octet but unstable because -1 FC on atom with low EN

Question 10

Electron Donating Groups

Answer 10

Atoms/groups of atoms with low EN (alkyl groups).

-EDGs minimize the effect of a + charge

Question 11

Electron Withdrawing Groups

Answer 11

Atoms/group of atoms with high EN (O, N, F, Br, Cl, etc.).

-EWGs minimize the effect of a - charge.

Question 12

Stability of carbocations

Answer 12

3 > 2 > 1 > methyl

• More EDGs (alkyl groups) => more stable
• More EWGs (EN atoms) => less stable
• If a carbocation has resonance then the molecule is more stable (the + or - charge is delocalized).

Question 13

Stability of Carbanions

Answer 13

methyl > 1 > 2 > 3

• More EWGs => more stable
• More EDGs => less stable
• If a carbanion has resonance then the molecule is more stable (the + or - charge is delocalized)

Question 14

Acidity

Answer 14

Molecule with a more stable to conjugate base => more acidic.

• Increasing EN of the atom that loses the H (and gets a -charge as a conjugate base).
• Increasing resonance of conjugate base (delocalizing the -charge).
• Increasing size/polarity of the atom that has a - charge (HCl > HF)

Question 15

Basicity

Answer 15

Molecule with a more stable conjugate acid = more basic.

• Opposite trends as acidity (i.e. decreasing EN of atom that gains H; smaller atom that gains the H atom).
• Less resonance of base (CH3CH2NH2 > C6H5NH2).
• Atomic groups that are poor LGs are in general stronger bases.

Question 16

Nucleophile

Answer 16

Donates a pair of electrons to an electrophile, forming a bond (Lewis base).

• Pi bond or atom with a lone pair.
• Likes and attacks positively charged species (“nucleo” “Phile”).

-Common nucleophiles:
Halides (I-, Br-, etc.); OH-, RO-, NH3, NH2-, CN-

Question 17

Nucleophilicity increases with…

Answer 17

• Increasing negative charge of atom that acts as nucleophile (NH2- > NH3).
• Increasing size/polarity of atom (I- > Cl-; SH- > OH-).
• Decreasing EN because better at sharing its pair of e-.
• Generally, strong bases are good nucleophiles (Bronsted-Lowry base is a nucleophile that attacks and forms a bond with a hydrogen).
• Decreasing steric hindrance.

Question 18

Electrophile

Answer 18

Electron deficient species that accepts an electron pair by forming a bond with a nucleophile.

-Lewis acid
-Has + or partial+ and/or an incomplete octet
-Common electropholes:
H+, H3O+, BF3, Partial+C

Question 19

Leaving group

Answer 19

Better LG= more stable existing on its own (apart from the molecule that it leaves) and better at holding the e- (and the negative charge) that it receives.

-Weak bases (conjugates or strong acids) = good LG