Intro to Organic Chem Flashcards by Monique Yuan

What does bond order describe?

whether a covalent bond is single, double or triple

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What is the bond order of a single, double, and triple bond?

single –> bond order = 1
double –> bond order = 2
triple –> bond order = 3

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How many sigma bonds and/or pi bonds are found in a single bond?

1 sigma bond

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How many sigma bonds and/or pi bonds are founc in a double bond?

one sigma and one pi

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How many sigma bonds and/or pi bonds are found in a triple bond?

one sigma bond and 2 pi bonds

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TRUE or FALSE: potential energy is directly proportional to bond strength.

FALSE –> potential energy is inversely proportional to bond strength

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TRUE or FALSE: bond length is inversely proportional to bond strenght.

TRUE

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What is the formula for formal charge?

formal charge = (# of valence electrons in free atom) - (# of electrons in lone pair) - (# of bonds)

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TRUE or FALSE: In a Lewis diagram, the central atom is usually the least electronegative.

TRUE

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What are 4 things to look out for when determining the MAJOR resonance structure?

full octet
minimum number of formal charges
negative FC on electronegative atoms
minimum separation between opposite FCs

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What does VSEPR stand for?

valence shell electron pair repulsion

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TRUE or FALSE: lone pairs contribute to the determination of the geometry of a molecule, using VSEPR theory.

TRUE

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Provide the number of groups, bond angle(s), central atom hybridization for the following basic geometry:

Linear

(note: number of groups = number of atoms and lone pairs connected to the central atom)

number of groups = 2
bond angle = 180
hybridization = sp

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Provide the number of groups, bond angle(s), central atom hybridization for the following basic geometry:

Trigonal planar

(note: number of groups = number of atoms and lone pairs connected to the central atom)

number of groups = 3
bond angle = 120
hybridization = sp2

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Provide the number of groups, bond angle(s), central atom hybridization for the following basic geometry:

Tetrahedral

(note: number of groups = number of atoms and lone pairs connected to the central atom)

number of groups = 4
bond angle = 109.5
hybridization = sp3

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Provide the number of groups, bond angle(s), central atom hybridization for the following basic geometry:

trigonal bipyramidal

(note: number of groups = number of atoms and lone pairs connected to the central atom)

number of groups = 5
bond angle = 90, 120
hybridization = sp3d

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Provide the number of groups, bond angle(s), central atom hybridization for the following basic geometry:

octahedral

(note: number of groups = number of atoms and lone pairs connected to the central atom)

number of groups = 6
bond angle = 90
hybridization = sp3d2

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TRUE or FALSE: each bond in a double bond contributes individually to the hybridization of an atom.

FALSE –> double bonds do NOT contribute individually to hybridization

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If an atom has a choice between sp2 and sp3, it chooses _______.

sp2

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What is the geometrical name for a molecule that has 2 groups and alone pair?

bent

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What is the geometrical name for a molecule with 2 lone pairs and 2 groups?

bent

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TRUE or FALSE: electron delocalization decreases a molecule’s stability.

FALSE: electron delocalization INCREASES a molecule’s stability

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What is the name of the rule used to determine if a compound is aromatic? Provide the guidelines.

Huckel’s Rule…a molecule is aromatic if it is:

planar
cyclic
fully conjugated (alternating single and double bonds)
contains a total of 4n+2 pi electrons (where n = 0, 1, 2, 3, etc.)

note: all carbons must be sp2 hybridized

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TRUE or FALSE: if an atom has both a lone pair and a double bond, the lone pair does not contribute to aromaticity.

TRUE –> note that the double bond contributes to aromaticity

TRUE or FALSE: if an atom has 2 lone pairs, both lone pairs contribute to aromaticity.

FALSE --> only one lone pair will contribute to aromaticity

Define chiral.

any object that CANNOT be superimposed on its mirror image

what are the 2 structural features of a stereogenic centre (chiral carbon)?

1. the carbon will be sp3 hybridized (tetrahedral) | 2. the carbon will be bound to 4 DIFFERENT atoms or groups

In a fisher projection, what is the difference between the vertical and horizontal lines?

``` vertical = going into the page horizontal = coming out of the page ```

What is a constitutional isomer?

structural isomers (different atom connectivity)

What is a stereoisomer?

isomer with same atomic connectivity, but different arrangement in space

What is a conformer/conformational isomer?

isomer with single bond rotation

Arrange the following from least stable to most stable conformer: gauche anti eclipsed

eclipsed < gauche < anti

What letter of the alphabet designates a cis-alkene?

What letter of the alphabet designates a trans-alkene?

If there are 3 substituents in an alkene isomer, how do you designate whether it is cis or trans?

Look for the higher priority group on each side of the double bond

What is an enantiomer?

mirror image that cannot be superimposed i.e. same connectivity but opposite configuration at EVERY chiral centre

What are the 4 properties of enantiomers to keep in mind for the MCAT?

enantiomers: 1. have opposite stereochemistry at ALL stereocenters 2. have identical physical properties (bp, solubility, polarity) 3. react identically in most environments 4. react differently in a chiral environment

How must the lowest priority atom/group be arranged on a molecule, when designating R and S configuration of a chiral centre?

the lowest priority atom/group must be pointing into the page

Since enantiomers share identical physical properties, how can we tell them apart?

rotation of plane-polarized light

Define dextrorotary. Is it designated with (+) or (-)?

(+) | rotate plane-polarized light to the right (clockwise)

Define levorotatory. Is it designated with (+) or (-)?

(-) | rotate plane-polarized light to the left (counter-clockwise)

What is a racemic mixture?

a 50:50 mixture of 2 enantiomers

TRUE or FALSE: racemic mixtures result in a net rotation of plane-polarized light.

FALSE --> the 50:50 cancels out the rotation direction, so there is NO NET rotation

What is one method of separating racemic mixtures?

React the enantiomers with another chiral molecule to produce diastereomeric salts.

What are diastereomers?

stereoisomers that are not mirror images | must have at least one different stereocenter and at least one same stereocenter

How do you calculate the maximum number of stereoisomers that a given molecule can have?

2^n n = # of chiral centers

What is a meso compound?

compound that contains a minimum of 2 chiral centers but is itself ACHIRAL

TRUE or FALSE: meso compounds rotate plane-polarized light

FALSE --> meso compounds do not rotate plane-polarized light

What are the 3 questions you should ask yourself when checking for meso compounds?

1. Is there a minimum of 2 stereocentres? 2. Is there a plane of symmetry? 3. Are both halves of the molecule mirror images of each other (cannot be superimposed)?

Thin layer chromatography, paper chromatography, and column chromatography separate mixtures based on: a) size b) specific affinity c) boiling point d) polarity e) charge

d) polarity

Gas chromatography separate mixtures based on: a) size b) specific affinity c) boiling point d) polarity e) charge

c) boiling point

Size-exclusion separate mixtures based on: a) size b) specific affinity c) boiling point d) polarity e) charge

a) size

Ion-exchange chromatography separate mixtures based on: a) size b) specific affinity c) boiling point d) polarity e) charge

e) charge

Affinity chromatography, paper chromatography, and column chromatography separate mixtures based on: a) size b) specific affinity c) boiling point d) polarity e) charge

b) specific affinity

What is the difference between stereospecific and stereoselective reactions?

stereospecific --> only create one kind of enantiomer | stereoselective --> favour one type of enantiomer, but still have some of amount of the other

What is the name of the extraction technique used to separate a mixture of enantiomers by producing diastereomeric salts?

resolution

In a liquid-liquid extraction, which layer is found on the top and which layer is found on the bottom? Describe the contents of the layers.

top = organic = large/less polar molecules bottom = aqueous = small/more polar molecules, strong acids and bases, salts