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Orgo 2 > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

What type of waves does infrared spectroscopy measure?

A

Infrared waves

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2
Q

What does IR spectroscopy measure

A

The bond vibration frequencies; helps determine the structure of a compound.

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3
Q

Where is the fingerprint region?

A

Below 1500. Ignore this part of the graph.

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4
Q

What is the cm-1 of a carbon carbon single bond (sp3 hybridized)

A

1200 cm-1
Irrelevant because it falls within the fingerprint region

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5
Q

What is the cm-1 of a C-C double bond (hint: sp2 hybridized)

A

1660 cm-1

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6
Q

What is the cm-1 of a C-C triple bond? (Hint: sp hybridized)

A

<2200 cm-1. Usually will be 2140 to 2150.

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7
Q

What is the cm-1 of a conjugated C-C double bond (ex. aromatic carbon)

A

Approximately 1600 cm-1. Resonance/conjugation LOWERS the frequency compared to an isolated C-C double bond.

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8
Q

What is the cm-1 of a C-H bond on an sp3 hybridized C? (Hint: Alkane)

A

2800-3000 cm-1. Broad band

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9
Q

What is the cm-1 of an C-H bond on an sp2 hybridized C? (Hint: Alkene)

A

3000-3100 cm-1. HINT: There will also be a long stretch at 1642 cm-1 for the double carbon bond.

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10
Q

What is the cm-1 of an C-H bond on an sp hybridized C?

A

3300 cm-1. SHARP indent on graph. HINT: Will only show up with an asymmetrical alkyne. If the alkyne is symmetrical there is no peaks at 2119 cm-1 for the triple bond, or for the C-H stretch.

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11
Q

What is the shape of the O-H bond?

A

Around 3300 cm-1, with a broad and rounded tip.

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12
Q

What is the measurement for amines (N-H)?

A

3300 cm-1.

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13
Q

What do the peaks look like for a primary amine (RNH2)?

A

Broad with two sharp spikes, since there are two hydrogrens

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14
Q

What does the peak look like for a secondary amine (R2NH)?

A

Broad with one sharp spike.

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15
Q

What does the peak look like for a tertiary amine (R3N)?

A

There is no peak! Since there are no hydrogens the IR does not show a tertiary amine.

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16
Q

What is the measurement of a C-O double bond?

A

Simple ketones, aldehydes, and carboxylic acids absorb around 1710 cm-1.

17
Q

Which of the three molecules with carbonyl groups (ketones, aldehydes, and carboxylic acids) has two C-H signals?

A

Aldehydes. Both are around 2700 and 2800 cm-1.

18
Q

What is the measurement of the O-H stretch in carboxylic acid?

A

2500-3500 cm-1. Both a peak for the C-O double bond (1710 cm-1) plus this OH must be present to identify the carboxylic acid.

19
Q

What is the measurement of esters (C=O + R/ OR)

A

Around 1735 cm-1.

20
Q

What is the measurement of a C-N bond?

A

Around 1200 cm-1.
Irrelevant because its in the fingerprint zone

21
Q

What is the measurement of a C-N double bond?

A

1660 cm-1.

22
Q

What is the measurement of a C-N triple bond?

A

> 2200 cm-1. A nitrile (C-N triple bond) is GREATER than a C-C triple bond.

23
Q

What are the top three strongest frequencies?

A

Alcohol(OH), amine (NH), and alkyne (triple C-C bond with the C of interest attached to a hydgrogen. Recall that this alkyne must be asymmetrical). All measure at around 3300 cm-1.

24
Q

What does a hydrogen’s chemical shift depend on?

A

The atoms that are next to the carbon attached to the hydrogen. It is measured in ppm.

25
Q

What is the chemical shift of a methyl proton?

A

0.9

26
Q

What is the chemical shift of a methylene proton (C is attached to one other H and one other C).

A

1.3

27
Q

What is the chemical shift of a methine proton? (C is attached to three other C).

A

1.4

28
Q

What is the chemical shift of a methyl ketone?

A

2.1

29
Q

Chemical shift of a proton attached to a C next to a halogen?

A

3-4

30
Q

Chemical shift of a vinyl proton? (C-C double bond/alkene)

A

5-6

31
Q

Chemical shift of an aromatic hydrogen?

A

Anywhere from 7-8. The aromatic rings makes the ppm increase greatly

32
Q

Chemical shift for the proton of an aldehyde?

A

9-10

33
Q

Chemical shift for the proton of an alcohol?

A

Variable, about 2-5

34
Q

Chemical shift for the proton of an amine?

A

Variable, about 1.5-4

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