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chemistry > BS21012 Core Lab Skills 2A > Flashcards

BS21012 Core Lab Skills 2A Flashcards

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1
Q

A carboxylic acid and an alcohol form to make…

A

An ester and water

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2
Q

the reaction to make an ester is called…

A

Acid catalysed ester formation

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3
Q

The reverse reaction of ester formation is called…

A

Acid catalysed ester hydrolysis or enzyme-catalysed ester hydrolysis

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4
Q

orange peel and pig liver esterases are a class of esterases belonging to a family called…

A

Carboxylesterases.

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5
Q

Pig liver esterase is a…

A

serine hydrolase

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6
Q

What are the two key steps in serine hydrolase’s mechanism of ester hydrolysis…

A

Nucloephilic addition of serine to the carbonyl group of the ester.
Collapse of the tetrahedral intermediate

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7
Q

What is the “regeneration of the catalytic triad”…

A

The covalent adduct with the substrate is hydrolysed in a reaction with water that is catalysed by the proximity of the nucleophilic imidazole ring of histidine

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8
Q

Orange peel esterase is a pectin-esterase which is a(n)…

A

an enzyme that catalyses the hydrolysis of pectin into pectate and methanol

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9
Q

Pectin is a polysaccharide characterized by…

A

Repeated units of Methylated galacturonic acid (Gal A)

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10
Q

A molecule made of repeated units of Methylated galacturonic acid (Gal A) is called…

A

Pectin (polysaccharide)

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11
Q

give examples of processes in which de-esterification of pectin is important…

A

Cell wall metabolism
Fruit ripening
Pollen germination
Plant resistance to pathogen attack

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12
Q

Where can acetylcholine esterases be found… (2 places)

A

in the postsynaptic cell membrane of the neuromuscular junction
Cholinergic neurons in the brain

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13
Q

What do Acetylcholine esterases do…

A

It hydrolyses acetylcholine, a neurotransmitter, into choline and acetate

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14
Q

What have the reverse inhibitors of acetylcholine been shown to interact with… (diseases)

A

Alzheimer’s disease, Myasthenia grans, glaucoma.

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15
Q

Irreversible inhibitors of acetylcholine are known to be involved in…

A

toxins, insecticides, and nerve agents

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16
Q

What are the symptoms of acute poisoning from acetylcholine inhibitors…

A

Agitation, muscle weakness, sweating, respiratory failure, confusion/ unconsciousness, convulsions and/or death

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17
Q

Infra red radiation…

A

excites the stretching vibration of bonds and deformation vibrations of bond angles

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18
Q

What must a bond have for IR to have an effect…

A

The bond must have a dipole-dipole attraction

19
Q

IR has a ____ wavelength than than visible light and ____ energy

A

Greater wavelength and less energy

20
Q

An IR spectrum shows…

A

Characteristics for a single molecule

21
Q

What do the peaks in an IR spectrum represent

A

The peaks represent specific functional groups

22
Q

What do the X and Y axis show on an IR spectrum graph

A

The X-axis shows wavenumber (cm-1), and the Y-axis shows IR absorbance

23
Q

What are the 2 main descriptions of IR peaks…

A

Sharp or broad (sp or b)

24
Q

What are the 4 classifications of intensity in IR peaks…

A

Very strong (VS) >90% absorption
Strong (S) 70-90% absorption
Medium (M) 50-70% absorption
Weak (W) <40% absorption

25
Q

Where X is an element what is the IR stretch of X-H

A

3500-3100cm-1

26
Q

Give examples of X-H stretches, a description of their peak, the intensity of the peak, and the name of the group…

A

O-H, S, B, alcohols and phenols
O-H, S, VB, Acids
N-H, S, Sp, 1’ amines/amides or 2’ amines/amides

27
Q

C-H stretch is in what range on an IR spectrum

A

3300-2700cm-1

28
Q

Name the three different groups of C-H groups in IR

A

Aromatic - 3150-3000cm-1, W-M
Alkenic - 3050-2950cm-1, W-M
Alkanic - 2950-2850cm-1, W-M

29
Q

Name the two other types of C-H stretch (irregularities)

A

Terminal Alkynes (if the weak peak of C-C) (a triple bond is found near 2200cm-1), 3300cm-1, S

Aldehyde - 2850-2700cm-1, W-M, O=C-H bond (two peaks)

30
Q

What is the range of the C=O stretch

A

1850-1550cm-1

31
Q

What are four examples of C=O stretches on an IR spectrum

A

Anhydride - 1850-1800cm-1, VS, (second peak at 1750)
Carboxylic acid Halide - 1820-1750cm-1, VS
Ester - 1750-1710, VS
aldehyde - 1740-1690, VS (only if C-H peaks present)

32
Q

Name the other four examples of C=O stretches

A

Ketone - 1730-1650cm-1, VS
Carboxylic acid - 1720-1680cm-1, VS
Carboxylic acid anion, 1650-1550cm-1, VS
Amide - 1670-1630cm-1, VS, (2 bonds, the second is at 1560-1510cm-1)

33
Q

What is an key observation about the overlapping in the IR spectrum

A

There can be overlaps between the intensity readings, the structure is then determined using knowledge of the shape and structure of molecules.

34
Q

For a compound to be classed as aromatic it must have the following features

A

A C-H stretch at 3150-3000cm-1, W-M (usually weak)

A C-C stretch at 1600-1500cm-1, W-S, (sharp but 1600 is not always present)

A C-H deformation at 900-600, M-S (usually strong)

35
Q

if a compound is not aromatic in IR it must be…

A

Aliphatic (linear)

36
Q

What are the key characteristics of an Aliphatic molecule

A

If the C-H stretch absorptions are al below 3000cm-1 and there are no strong series at 900-600cm-1, the compound is aliphatic and contains no C-C bonds

37
Q

If an -OH group is found at 3500-3100cm-1 what are the two types of compound it could be apart of

A

Alcohol or phenol

38
Q

if there is an OH group at 3500-3100cm-1 what is the range the C-O stretch will be found in for it to be an alcohol or a phenol

A

1250-1050cm-1

39
Q

what is the intensity value for a phenols C-O stretch

A

1200cm-1, VS

40
Q

what are the three different intensities of alcohols C-O group and what do they correspond to

A

Primary, secondary and tertiary alcohols all have different intensities

Primary, near 1050cm-1, VS
secondary, near 1100cm-1, VS
tertiary, near 1150cm-1, VS

41
Q

What is the difference in IR between amines and amides

A

if a sharp peak(s) is found at 3500-3300cm-1 then the conformation of an amide will be seen through a C=O stretch at 1670-1620cm-1.
if this is not present then it is an amine

42
Q

What are the distinctions between 1’ and 2’ amines

A

1’ amines normally show two N-H peaks

2’ amines only show one N-H peak

43
Q

what are the intensity ranges for amines

A

N-H deformation, 1650-1500cm-1, M, (1’ amines)
N-H deformation 1580-1500cm-1, M-W, (2’ amines)
C-N stretch, 1350-1270cm-1, M-S (not always seen)

44
Q

How are carbonyl compounds identified

A

They are identified through the expected additional features either in the primary or confirmatory region

chemistry (2 decks)

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