ch. 1 - structure determines properties (part...

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ORGANIC - CAREY 10E

CH. 1 - STRUCTURE DETERMINES PROPERTIES (PART 2)

CONCEPT: CONDENSED STRUCTURES

The condensed method is a common way to describe the _________________________ of a molecule using only text.

● Know how to quickly interconvert between __________________ and condensed

EXAMPLE: Full Condensed Structure

EXAMPLE: Condensed Mixed Structure

PRACTICE: Convert the following condensed structures into bondline

CH2Br(CH2)3CH(CH2CH3)2

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CONCEPT: INDEX OF HYDROGEN DEFICIENCY (STRUCTURAL)

A saturated molecule is any molecule that has the maximum number of hydrogens possible for its chemical structure. The

rule that we use for this is _____________.

● Any molecule that has less than __________ number of hydrogens is considered to be __________________.

EXAMPLE: How many hydrogens must the following carbon skeletons contain to be saturated? Are they missing any?

IHD rules give us the ability to quickly determine which molecules are more saturated and which molecules are less

saturated with hydrogen.

● 1 IHD = Compound is missing ___ hydrogens.

□ Rings/Double bonds = _____

□ Triple Bonds = ______

EXAMPLE: What is the degree of unsaturation of the following compounds?

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CONCEPT: INDEX OF HYDROGEN DEFICIENCY (MOLECULAR FORMULA)

□ Molecular Formula:

- When given only the molecular formula of the molecule use the following rules.

(Theoretical # H’s – Actual # H’s) / 2 = IHD, where: ● H / X = _______ ● O = ______ ● N = ______

EXAMPLE: What is the IHD for each of the following compounds?

a. C4H7Cl

b. C6H7N

c. C7H12O2

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CONCEPT: CONSTITUTIONAL ISOMERS

Constitutional isomers are molecules that have identical molecular formulas (all the same atoms), but have

different _______________________. You will be asked to compare molecules and determine how they are related.

EXAMPLE: How are the following two compounds related?

A) Identical Compounds

B) Constitutional Isomers

C) Different Compounds

Steps to solve Constitutional Isomer Problems:

Step 1. (Are the atoms all the same?) Count non-_______________ atoms and IHD in both compounds

- If not exactly the same, they are ____________________________

- If the same, then go to step 2

Step 2. (Are the atoms all connected the same?) Look for a _____________ atom, then count bonds from there.

-If not exactly the same, they are _______________________________

-If the same, then they are _____________________________

EXAMPLE: How are the following sets of compounds related?

A) Identical Compounds A) Identical Compounds

B) Constitutional Isomers B) Constitutional Isomers

C) Different Compounds C) Different Compounds

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CONCEPT: RESONANCE STRUCTURES

Resonance theory is used to represent all the different ways that the same molecule can distribute its electrons.

● Atoms ____________ move! The only thing that moves is ______________________

● ________ of these contributing structures will be a realistic representation of what the molecule actually looks like

Rules:

● Use curved arrows to represent electron movement

● Use double-sided arrows and ________________ to link related structures to each other

● Arrows always travel from region of ___ electron density to ___ electron density

● The net charge of each structure must be _____________________

EXAMPLE: Common forms of resonance

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PRACTICE: Draw all of the contributing structures for the following molecules

a.

b. c.

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CONCEPT: RESONANCE HYBRIDS

The resonance hybrid represents the mathematical combination of all the contributing structures

● It indicates where the resonating electrons within the molecule are _____________________ to reside

EXAMPLE: Isocyanate Resonance Hybrid

CONCEPT: MAJOR CONTRIBUTORS

Often one of the resonance structures will be more _________ so it will contribute to the __________ more than the others.

Major contributors will often have the following characteristics:

● _______________ structures are almost always more stable than charged ones

□ If possible, every atom should fill its ___________

□ Use electronegativity trends to determine best placement of charges

EXAMPLE: Isocyanate major contributor

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PRACTICE: Draw all of the contributing structures for the following molecules. Label the major contributor if applicable and draw the resonance hybrid.

a.

b.

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CONCEPT: HYBRID ORBITAL THEORY

The Aufbau Principle states that electrons fill orbitals in order of increasing energy. If carbon has only two unfilled orbitals,

why does it like to make 4 bonds?

EXAMPLE: Carbon sp3 Hybridization

● Many atoms prefer to blend some of their 2nd shell orbitals together to make new _________________________ orbitals

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CONCEPT: HYBRIDIZATION SUMMARY

Hybridization can be predicted by the determine the number of ________ _________ on an atom

□ Where a bond site is equal to any _________ or _________ ___________

EXAMPLE: Predict the hybridization of the following reactive intermediates

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CONCEPT: MOLECULAR GEOMETRY

Molecular geometry is based on VSEPR theory: “Bond sites will ____________ each other as much as possible.”

□ The molecular geometry predicts what shape the hybridized atom will have.

EXAMPLE: Predict the hybridization and molecular geometry of the following selected atoms:

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PRACTICE: Determine the hybridization and molecular geometry of the following selected atoms:

a.

b.

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CONCEPT: ELECTRONEGATIVITY

Chemical bonds are formed when the sharing of valance electrons between two or more atoms takes place.

● The _____________ of sharing will determine the identity and strength of the chemical bond.

● An unequal sharing of electrons in one direction along a bond is called a __________ _____________ (______)

● The charge between any two bonded atoms is related to their difference in electronegativity

Generalizations:

● Bonds to carbon and hydrogen are always _______________

● Bonds between two identical atoms are always _________________

□ Adjacent atoms on the periodic table are _____________

□ Lone pairs are ____________

● ________ ________________ exist when atoms have asymmetrical dipoles

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PRACTICE: Which of the following molecules contain dipoles? Which contain net dipoles?

PRACTICE: Which of the solvents below is apolar? Which is polar?

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CONCEPT: FUNCTIONAL GROUPS

● We can group several millions of different molecules into subsets of similar _________________________

1. Hydrocarbons

● All carbon groups regardless of size can be symbolized using an _______ group.

● When an alkane is attached to a greater carbon chain, it is given an ________ suffix. (i.e. __________ group)

● Carbons are given a “degree” based on how many other ____________ they are attached to

□ Hydrogens possess the __________ degree as the carbon they are attached to

□ Degrees are expressed as primary, secondary, tertiary and quaternary (1⁰, 2⁰, 3⁰, 4⁰)

EXAMPLE: Determine the degree of the indicated carbons and hydrogens

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2. Alkyl Halide _________

● Any –R group directly attached to a halogen.

● The degree of alkyl halide is determined the same way as __________________

The carbonyl ____________ is NOT a functional group, but it is a major component of many functional groups

3. Alcohol ____________ 6. Carboxylic Acid ______________(_________) ● Degree of alcohol is determined the same ● The acid of organic chemistry way as ____

4. Amine ______________ 7. Amide _______________(___________)

Degree of alcohol is determined the same ● Degree of alcohol is determined the same way as ____. way as ____.

5. Ether __________________ 8. Ester __________________(___________)

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9. Carbonyls

The term “ carbonyl” is not the proper name of the functional groups because the functionality of the group depends on its location on the carbon chain.

.

● Ketone ______________(__________) ● Aldehyde ______________(__________)

- _______________carbonyl group - _______________carbonyl group

10. Nitrile ________________

11. Benzene

● Directly attached to –R group _______________ (_________)(_____)

● Extra CH2 between –R group _______________ (_____________)(_____)

EXAMPLE: Identify all the functional groups in the following compound. Show degrees where applicable.

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12. Other Carbonyl Compounds

● Acyl Chloride (__________) ● Anhydride (_______________)

13. Sulfur Compounds

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PRACTICE: Identify all the functional groups in the following compound. Show degrees where applicable.

a.

b.

c.

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CONCEPT: THE MECHANISM- REACTIVITY

The currency of organic chemistry is ____________________________ ● Stability and reactivity generally have an ___________________ relationship. ● The 4 common indicators of reactivity: 1. ____________________________ 2. ____________________________

3. ____________________________ 4. ____________________________ EXAMPLE: Identify which of the following molecules would be expected to be reactive. We can categorize almost all reactive molecules into two massive subtypes. These will display similar behaviors.

● Negatively charged species are known as ___________________

● Positively charged species are known as ____________________

The side of the dipole with the ______ bonding preference can be used to predict nucleophilicity or electrophilicity

EXAMPLE: Identify which of the above molecules are nucleophilic or electrophilic

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CONCEPT: THE MECHANISM- ELECTRON MOVEMENT Reactive molecules share electrons to become more stable. _________ are used to show which direction they are going.

● Arrows always move from regions of _________ electron density to _________ electron density ● By that logic, _________________________ must always attack ____________________________ ● Each attacking arrow represents ____ electrons being shared. Replace that arrow with a new ____ - __________ EXAMPLE: Determine the initial direction of electron movement by drawing the first arrow of each mechanism: a. b. c.

□ Bond breaking is sometimes also required in mechanisms, but only when it is required to preserve octets.

There are two ways to break chemical bonds: EXAMPLE: Identify which of the above reactions require bond breaking and/or more arrows to satisfy all octets.

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CONCEPT: ACID and BASE DEFINTIONS

Before we get started: Remember your strong six!

(HCl, HBr, HI, HNO3, H2SO4, HClO4)

□ Lewis definition: Same as ________________ □ Brønsted-Lowry definition:

● Acid is an electron pair ____________ ● Acid is a proton ___________

● Base is an electron pair ____________ ● Base is a proton ___________

EXAMPLE: Properly identify the following molecules:

a. b. c.

d. e. f.

Equilibrium: A base will always attack an acid to produce _______________________ in the following chemical pattern:

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PRACTICE: Move electrons using arrows to predict and label the products of the following reaction:

a.

b.

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CONCEPT: EQUILIBUIM CONSTANT and pKa ●In general chemistry, we used pH to measure __________________________________

● In organic chemistry, we use _______ to measure the tendency for a molecule to _______________________________

□ Strong acids have a _____ dissociation constant (they _______________ dissociate in aqueous solution)

□ Weak acids have a _____ dissociation constant (they ________________ dissociate in aqueous solution)

● p = Ka = (

) Therefore, the ____ Ka, the _____ the pKa

EXAMPLE: Calculate the pKa’s of the following acids and indicate which is the stronger acid.

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CONCEPT: pKa VALUES We can use pKa values to help us determine the relative acidity of common organic molecules. EXAMPLE: Identify all of the relevant pKa values for the indicated protons. Rank them in order of increasing acidity. PRACTICE: Rank the following organic compounds in order of increasing pKa

PRACTICE: Rank the following organic compounds in order of increasing acidity

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CONCEPT: ACID and BASE EQUILIBRIUM Ultimately, we can use pKa information to determine the overall direction and favorability of an acid base reaction.

STEPS: 1. Identify the Lewis acid and base

● Many times charges or a known acid will be present (+)___________ (-)___________

● Dissociate ALL spectator ions, these are the cations _______, _______ and _______

● If both compounds are still neutral, assign the one with the lowest pKa as the acid

2. Label the conjugate acid and base

3. Compare the acidity/pKa of the Lewis Acid to the ______________. Must go from ___________ to __________

EXAMPLE: Would the following reactions go to the right or the left? Label ALL species. Draw arrows in the correct direction.

a.

b.

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CONCEPT: FACTORS AFFECTING ACIDITY- ELEMENT EFFECTS There are 5 major factors of acidity. We use these factors to determine relative acidity in the following two situations: 1. pKa information is _____________________ for a molecule

2. The pKas of two molecules are ________________ to make a determination of highest acidity.

□ When analyzing these 5 factors of molecules, look at the stability of the ________________________ ____________.

● The more stable the _______________________, the more willing the acid will be to donate a proton.

1. Element Effects:

● The element effects determine how loosely or strongly a particular element bonds with ____________

● We can use these effects to compare different protonated elements to each other. (i.e. NH3 vs SH2)

● Consists of two trends:

1. Electronegativity – the stronger the electronegativity, the more willing to accept a lone pair.

2. Size – the bigger (squishier) the atom, the more willing it will be to accept a lone pair.

EXAMPLE: Without using pKa values, which of the following pairs is more acidic?

1. NH3 or SH2 2. H2O or CH4

3. 4.

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CONCEPT: FACTORS AFFECTING ACIDITY- INDUCTIVE EFFECTS

Inductive effects describe the stabilizing properties that __________________________ atoms NOT CONNECTED to the

acidic hydrogen have on the overall acidity.

● Whenever a charge can be ________________ over more than one atom, the more stable that charged species will be .

● Electronegative entities on other parts of the molecule can help “spread out” the negative change of the conjugate base

through inductive effects.

EXAMPLE: Draw rough sample electron clouds over the following pairs of conjugate bases of their respective alcohols. Which is more stable? Which alcohol would have had the lower pKa?:

Factors that increase inductive effects:

1. Strength of the electronegative entities ________________________________________

2. Number of electronegative entities ___________________________________________

3. Proximity of electronegative entities ___________________________________________

EXAMPLE: Without using pKa values, which of the following pairs is more acidic?

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CONCEPT: FACTORS AFFECTING ACIDITY- OTHER EFFECTS Resonance Effects:

Definition: Whenever the donation of a proton leads to the formation of a possible ______________________________,

that conjugate base will be _________ stable, and the molecule will be a ___________ acid.

EXAMPLE: Which of the following pairs of acids would have the lower pKa? Explain why.

Hybridization Effects:

Definition: The more s-character in the acid, the closer to the nucleus extra lone pairs will be held to it, making the conjugate base ________ stable.

Acidity Trend = sp C – H ______ sp2 C – H ______ sp3 C – H

EXAMPLE: Which of the following hydrocarbons is the most acidic?

Steric Effects:

Particularly with alcohols, the more easily solvated the conjugate base is, the more stable it will be.

● The smaller the R group, the more ___________ the alcohol

● The bigger the R group, the more ___________ the alkoxide

EXAMPLE: Which of the oxides is the most basic?

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PRACTICE: Would the following reactions go to the right or the left? Draw the products and label ALL species. Provide the full mechanism. a. b.

c.

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ch. 1 - structure determines properties (part...

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